Denver Paramedics add enhanced ambulance markings

New reflective contour, door and hatch markings fitted by Denver Paramedics

Immediately after the 3rd Annual EMS Safety Summit held in Denver CO, Denver Paramedics retro-fitted enhanced reflective markings to their ambulance fleet. White vertical and baseline contour striping were added to the patient care compartment to clearly outline the ambulance body at night. The white reflective tape cannot be seen during daylight and therefore does not detract viewer attention away from the solid vehicle profile during the day. Under headlamp illumination at night, the contour markings along with the new door and hatch markings offer a clear image of the ambulance especially when the doors are open on the roadside.

The Denver changes are a great example of an inexpensive and easily completed retrofit that delivers a substantial increase in vehicle and crew safety during day-to-day ambulance operations. More information is available on the Ambulance Visibility website.

Ambulance Visibility website and AV Blog statistics for 2011

The yearly visitor statistics are in for 2011, They show that both the Ambulance Visibility website and the AV Blog have received over 50,000 visits between them during the 12 months. Much of the credit must go to the new AV Reference Library that for the first time brings together comprehensive links to the latest visibility /conspicuity research as well as other research resources from around the world.

The many documents and articles provided by David Green last year have been very popular as downloads, as have other several other documents sent in by Malcolm Palmer from the UK and Johan Granlund in Sweden. The Ambulance Visibility website continues to sustain a trustworthy and reliable knowledge base with detailed links to an ever-increasing library of international resources.

Stay tuned for some new additions in 2012; there will be an increasing emphasis on the new directions being taken within European conspicuity, plus a sure-be-controversial new discussion commentary that compares many different emergency vehicles and their marking layouts. As always, you will be kept up-to-date with current research and the latest news.

Thank you to all on the web who have taken the time to have a look at one or both of the Ambulance Visibility sites during 2011.

All the best for 2012 -  John Killeen

Announcing the new Ambulance Visibility Reference Library

 

The Ambulance Visibility Reference Library logo

It has always been exceptionally difficult to find accurate research without spending hours searching the internet.

 

The new Ambulance Visibility Reference Library brings visibility and conspicuity research documents and information together in the one place for the first time. The AV Reference Library provides links to a multitude of relevant documents and reports, including a large number of studies and articles that have not been previously available on the internet.  The important research work of David Green, an Australian engineer who was at the forefront of visibility and conspicuity research for emergency vehicles between 1970 and 1990 appears on the internet for the first time.

David Green’s research papers provided guidance to State and Territory emergency service organisations across Australia for many years with his studies and articles remaining an important cornerstone of vehicle conspicuity practise to the present day. You can read copies of his work CLICK HERE.

Documents and studies are catalogued in broad categories by subject and this makes the library resource very easy to use. New documents will continue to be added to the library over the next few weeks. Try the AV Reference Library for yourself – CLICK HERE

Chevron enquiry from Pikesville Fire Department

Upright chevron V markings on a Pikesville FD vehicle

In late November 2010, I received a blog comment from Capt. John Berryman from Pikesville Fire Department asking the following question about using upright chevrons on the rear of fire appliances rather than the inverted-V pattern. John also forwarded a photo of a Pikesville fire truck.

“Sirs, could you please reference any problems with using a standard V pattern for the reflective chevron markings on the rear. Not the inverted V pattern. Our department has installed a V pattern on the rear of one of our larger trucks and have come under question as to why. Somewhere a while back I read that the standard V pattern draws you attention to the standing vehicle much better then an inverted V pattern. Can you explain. Thanking you in advance.”

Thanks John – Here is a copy of my reply:

Background to Chevrons                                                                                                             Your question about upright V vs inverted V rear facing chevrons is not an easy one to answer. The earliest wide scale use of a large standardised chevron pattern took place in the UK when the Police forces placed them on vehicles in an attempt to reduce the incidence of rear-end collisions when police cars were stopped on motorways. This early chevron was a precursor to the Battenburg conspicuity marking designed a few years later. Up to this point most emergency agencies around the world had been using a narrow chevron band, diagonal striped band or small diagonal panels on the rear of their vehicles. In an attempt to reduce the rear-end collisions during the early nineties, UK police began placing a red and white striped chevron across the trunk lid of their sedan vehicles. They simply borrowed the chevron pattern from the usual roadside signs found in Britain and this also accounts for the current inverted orientation.

I have undertaken a considerable amount of research in an attempt to find a methodology as to why chevrons are oriented the way they are?  It is clear that chevrons originating in ancient heraldry can be oriented either way; as are chevrons used in military insignia. Most road signs use an inverted chevron or horizontal chevron shape as an indicator arrow pointing towards the required direction of travel. The only definitive document I have found with any explanation about this is the Guide to Hazard Markers  and published by Queensland Main Roads (Australia). This document outlines the rationale for particular chevron directions but it does not include an upright chevron pattern within the definitions.  

Adoption of chevrons for the UK Police Battenburg conspicuity design.           As a consequence of a need for enhanced high-conspicuity vehicles on the motorway and high-visibility policing off the motorway, the following operational requirement was formulated and developed by the UK Home Office; “To determine for police traffic patrol vehicles operating in a motorway environment a suitable common standard of markings which enhances, at a distance, conspicuity and recognition as a police vehicle.” Cutting a long story short – the Battenburg conspicuity pattern was developed for police sedans in the mid to late nineties. It made use of the new fluorescent retro-reflective materials that had just become available at the time. The Battenburg design came in two types:                                   

1. Full Battenburg – for use on sedans for motorways                                                                2. Half Battenburg – designed for use on sedans off-motorways in towns and on lesser roads. The development team acknowledged that the Full Battenburg pattern could exhibit camouflage effects when seen against the complex backgrounds found in towns away from the simpler motorway landscape.

The operational testing of Battenburg concentrated on the identification of the chequered blue/yellow side profile rather than the anti-collision chevron red/orange profile marked on the rear. In fact no independent testing of the chevron layout after separating it away from the Battenburg chequered vehicle design was ever undertaken. The development team simply borrowed the red/white inverted-V chevron pattern from the earlier police vehicles and combined it with the Battenburg trunk-mounted chevrons which were then altered to the new fluorescent colours. It was taken for granted that the new chevrons would reduce the rear-end collisions with police cars; collisions that had in fact been increasing during the previous years. The inverted-V orientation of the chevron was now formalised for the first time into the UK Police Battenburg design specification.

Research into Police vehicle rear-end collisions                                                    There are almost no publicly available figures issued by UK police that allow interpretation of the success or failure of chevrons in reducing rear end collisions. Only one group of researchers were given access to police statistics and they subsequently published the report An analysis of `Looked but failed to see accidents involving parked police vehicles’ This study by Langham, Hole, Edwards & ONeill examined police vehicles and the Looked But Failed To See phenomenon which led to the following conclusions:  

On a theoretical level, the accident data clearly demonstrate that high levels of conspicuity (in sensory terms) do not guarantee detection of a vehicle, a conclusion supported by the results of our two experiments. They also suggest that cognitive factors, such as drivers’ expectations, may play an important role in causing this kind of `looked but failed to see’ accident. Precisely which cognitive factors are involved include fatigue, false hypotheses, inattention or a combination of all of these remains to be determined by future studies? On a practical level, the results suggest that drivers of all vehicles that are stationary on a high-speed road should try to draw attention to the fact that their vehicle is motionless: parking at an angle is one way to achieve this.

This research demonstrated that the use of rear chevrons does not guarantee a reduction in rear-end collisions. During the testing simulations one test driver had actually collided with the rear of the simulated police vehicle fitted with red/yellow chevrons.

The Battenburg markings were then borrowed by other UK emergency services. The Ambulance Services in the UK translated the yellow/blue Battenburg pattern into a new green/yellow combination and added a full sized chevron panel to the rear of their ambulances. This is the point in time that the UK layout would later go on to popularise the chevron pattern on ambulances and fire trucks in overseas countries. Remember, no research had yet concluded that the chevron design reduced rear end accidents!

The Battenburg testing had taken place on sedans and not full sized truck modules. Initially the UK NHS ambulance services experimented with a four axis chevron (four distinct chevrons pointing to the centre) but this was soon changed to the inverted-V. The inverted-V chevron has now become the standard orientation by default and is based on the UK Battenburg designs. This design logic relates back to the direction of the descending arms on chevron road signs indicating that the required direction of travel is to the side and away from the sign. This format is based on a top-down scanning pattern used by most people when looking at a sign, whereas the upright-V pattern would require a bottom-up scanning pathway . Other UK emergency services picked up the Battenburg + chevron pattern and began using the markings across many different exotic combinations of low-vis colours. The only true Hi-Vis colour scheme for Battenburg is the police yellow and blue and for chevrons red/orange with yellow.

The chevron pattern overseas                                                                                                During the early 2000’s the popularity of the UK Battenburg and chevron patterns migrated to overseas countries. This rapid increase in the use of the design on emergency vehicles was in part due to: 

1. Emergency agency personnel overseas finding the pattern distinctly different and therefore attractive.  
2. Graphics companies beginning to pick-up the Battenburg design and dramatically modify the original UK Battenburg design (including the chevrons) in both size and colour.
3. A perceived safety factor that (unknown to most people) was as yet unproven
4. Promotion of the modified Battenburg schemes by overseas manufacturers on their new safety concept vehicles.
5. Finally – the adoption in the US of the chevron markings in NFPA 1901 as the recommended safety pattern for fire appliances.

This has led to “chevron creep” onto ambulances and other emergency vehicles in the US, including the borrowing of the standard UK yellow/blue police colours to represent other emergency agencies (especially EMS). The draft NFPA specification 1917 for ambulances now threatens to secure and formalise the Inverted-V chevron as the recommended baseline marking for all ambulances in the United States.

By default, the Inverted-V orientation will remain the international standard. As I explained earlier the only logic available for the Inverted-V appear to be the top-down scanning pattern and  the independent definitions provided by the Queensland Roads document. There is now an official and public expectation secured by several formal US and UK specifications that chevrons will be fitted:

1. As an inverted-V
2. Use only reflective and/or fluorescent red/orange or yellow.  
3. Chevrons at least 6″ (150mm) wide.
4. Be fitted to the rear of an emergency vehicle

I hope this summary provides some information about what has happened to the chevron pattern over the last few years. Unfortunately it appears that little support will be available for the upright-V chevron pattern as public opinion has quickly adopted the Inverted-V as the national standard. Not only will your agency vehicles be different to most others around the country but you will continue to receive criticism for not following the national guidelines, which although not mandatory, still carry substantial weight in both the industry and public arenas.

As stated throughout this summary, there appears to be very little concrete evidence confirming the design rationale or efficacy of chevrons in any orientation, but the pattern appears to have secured a formal position due to a perceived element of safety and through popular industry opinion. There is very little research available to assist you in making a decision concerning the alternate chevron design currently on your vehicles.  Also, have a look at the 3rd Annual Colorado Safety Summit presentation available in the downloads section on the AV website at http://www.ambulancevisibility.com …. the PowerPoint illustrates many of the details I have discussed.

Fire Rescue News – 70s throwback: Lime-yellow fire trucks fade out

Pinellas Park Fire Department has decided to change vehicle colour from yellow-green to deep red according to an article written by Anne Lindberg in The St Petersburg Times and reflects the personal view of at least 60% of the department’s firefighter’s. Subsequently, a second article,  published around the same time in Fire Rescue News (FRN)  is another genuine example of the growing trend for emergency services to uphold the traditionalist view to ignore and sublimate proven research. There is little doubt that the Pinellas Park firefighters are sincere in their choice to return to deep red coloured fire vehicles.

What is different about the Pinellas articles is that they discuss in great detail the reasons behind the majority decision in the ranks and return to the dark red coloured vehicles. The magazine articles refer to last year’s FEMA visibility study as a major influence in their decision to change colour. The articles from Pinellas are recommended reading as most emergency agencies usually just briefly announce their new vehicles to the press but very few agencies willingly provide valuable insight as to why they decided to change colour.

I recently mentioned in an online webinar presentation that followed the release of the FEMA Emergency visibility and conspicuity study that certain generalised statements and recommendations made within the study document may possibly be open to misinterpretation. Those same recommendations may well be repeated later to aid and substantiate an alternative viewpoint that is not best practise. This type of  misinterpretation is usually unintentional and quite predictably is the result of a broad-speaking FEMA report choosing to exclude the fine detail to maintain brevity. The main recommendation that was taken from the FEMA report and then quoted in the Fire-Rescue articles as the example used in the report of vehicle colour recognition. This statement referenced yellow school buses, US Postal Service vehicles (white), Fedex courier vehicles (white) and the UPS courier vehicles (black). It is certainly true to say all of these vehicles are easily recognised, due in part to the life experience of other drivers and national TV advertising.  The frequent stopping habits of the vehicle operators listed in the last sentence are well known to the public but the major differences are that these civilian vehicles are never driven at emergent speeds, don’t have to pass carefully through intersections against red lights or perform blocking manoeuvres on busy highways. Most of the vehicles in the example are actually coloured either white or yellow; all high-contrast safety colours. I don’t think however that you could possibly extend the safety analogy to the black UPS truck as being of a safer colour, although many police agencies with black & white cruisers may try to put up an argument based on the concept of recognition!

One of the fundamental principles of visual safety relates to the use of high-contrast colours on emergency vehicles and these colours may be combined with an element of flourescent colour to maximise conspicuity and visibility. The common high visibility colours are fluorescent green-yellow, chrome yellow or white (but white only if it is paired with a fluorescent colour). European agencies often use fluorescent reddish-orange colours on their vehicles where there is heavy snow cover over much of the year. While the red-orange colour performs very well during daylight hours it can deteriorate to become dark grey or black under low levels of illumination or at night. Many european agencies now combine red-orange with a yellow-green base colour.

Pinellas Park is switching to a deep [non-flourescent] red which turns dark-grey to black at night and can blend into the shadows during the day. The red fluorescent/reflective colour scheme (mentioned in the FEMA report and referred to in the Pinellas articles) was fitted to a trial Mercedes wagon by ICE Ergonomics (UK). The retro deep red colour chosen by Pinellas is totally different to the ICE reflective red Mercedes treatment mentioned in the FEMA report. An Air Services Australia comparison report available on the Ambulance Visibility website clearly shows the difference in conspicuity between a green-yellow and red airport fire vehicles. The high contrast colours are perceived in the peripheral vision much earlier than dark colours (read a vehicle approaching from the side or at an intersection) and they visually resist merging into the shadows like dark colours. Seeing and reacting earlier to an emergency vehicle leaves more time for other drivers to process an avoidance strategy.

Please read the articles, form your own opinion and post a reply with your views!

Emergency vehicle chevrons – the AV Blog series Part 2

Welcome back to Part 2 of the Chevron Blog.  This part will discuss the following topics:           

• Chevrons on current and future vehicle fleets
• Current fleet markings with chevrons on different vehicle styles
• Differing expectations of Police, Fire & Ambulance
• Battenburg and chevron markings
• Chevron colour

You may well ask; why all the fuss about fitting chevrons to vehicle fleet?  This single basic aspect is often overlooked when the time comes to decide about appling chevrons to all the different vehicles in your fleet. In some cases the move to fit chevrons is a voluntary decision within one organisation. In other situations it may affect a complete industry; this was the case when the NFTA in the United States recommended all fire appliances be fitted with chevrons that cover at least 50% of the rear-facing profile.            

This type of blanket requirement may have a few implications for some agencies but can present a difficult set of problems to others. In the case of the NFTA, the area of coverage was set at a minimum 50%, which was appropriate and allowed flexibility for the layout of the chevrons to fit different vehicles. If the coverage requirement had been set at 90%-100% then the recommendations would be impossible to implement by some fire departments because the unusual design of their vehicles would not allow the full coverage required.               

The question of vehicle layout and suitability must be asked of all new marking designs, not just when fitting chevrons. When a complete redesign of the organisational markings is anticipated then all the vehicles, both current and future, must be evaluated for suitability and the visual fitness of the vehicle to receive the new markings. This assessment should include any four-wheel-drives, ATV’s, aircraft, boats, motorcycles, personal transport (eg Segway’s), electric buggies and bicycles that may be operated the agency. The shape and visual profile of all transportation used must be able to carry the markings in a common format; otherwise the unifying identity of the new marking design will become confusing to the public. All efforts should be made to anticipate the type & shape of vehicles that will be purchased in future years, especially where extensive fleet changeovers are likely or a change of manufacturer is a real possibility.           

It is also important to recognise that some vehicles and aircraft have no operational need for chevrons. Sometimes the particular size & shape of vehicles means that chevrons just cannot be fitted. Personal transporters, bicycles and like vehicles move relatively slowly compared to cars and they usually do not need to be placed in a blocking position on a highway (like other emergency vehicles); as such, no chevrons are required. Sometimes the rear of the fire vehicle is asymmetrical with steps or closely spaced warning lights leaving little or no space for chevrons to be seen effectively. A flexible approach for national regulators is to provide either an exemption for different or unusual vehicles or allow for an alternative marking panel in a single colour (eg yellow, yellow/green or red) rather than the obligatory full chevron pattern.              

A blanket chevron policy can be a real problem when governing organisations apply mandatory provisions for standardised markings nationwide. These problems increase even further when the national mandate conflicts with any existing federal, state or municipal regulations that cause the new markings to clash with existing statutory vehicle safety markings. The authorities in the UK had to petition parliament to change the road regulations so emergency vehicles could display the new Battenburg design and colours. One benefit of the legislation review was the changes effectively prevented any non-emergency entity from displaying similar colours on their vehicles. Unfortunately, imitations of Battenburg in permitted colours are creeping onto the roads           

The compatibility of any new chevron design with existing vehicle markings is the always a major issue that needs to be addressed. Most emergency agencies value their corporate image and their agency vehicle marking scheme. However, it can be very tempting to change the colour of the chevrons to match the existing colours. There is also a common tendency to overlay large amounts of text information already displayed on the rear of the vehicle over the chevrons – you should resist both these urges and also minimise and limit the text so it is clearly legible!               

The addition of standard yellow & red chevrons to a vehicle needs to be assessed carefully. Some vehicle colours and marking schemes (especially red & yellow body markings) may be disrupted when the chevron patterns are added, leading to great confusion as the camouflage effect begins to take over. Closely supervise any graphic designers who may attempt to promote “looks over function”.             

Camouflage effects of red/yellow chevrons combined with Battenburg markings

 

The FEMA visibility report released last year was successful in illuminating a number of issues. The report investigators had to review the needs of the many different emergency agencies in the US and provide some generalised guidance. In doing so the report also recognised the major differences in the level of need for on-road conspicuity required by the three main emergency services: Police, Fire and Ambulance/EMS.             

The Police require a stealth aspect for some operations but afterwards those same stealthy vehicles may require an increased level of conspicuity during different stages of the operational timeline. This is not an easy issue to resolve for law enforcement agencies. Ambulance/EMS and fire agencies always share a common need for maximum visibility and conspicuity throughout the course of their daily work. This is unlike the Police who often need a progressive scale of visibility levels. A dark coloured police sedan or black & white cruisers could be marked with chevrons or the word POLICE on the rear in a matching colour (black reflective on black or white reflective on white) that will be almost unseen in daylight but reflectively active at night under headlight illumination for traffic stops. Sometimes less than optimum safety markings can disguised as common stripes or decoration as a compromise.             

The Battenburg marking scheme in the UK provided the opportunity and initial momentum for the adoption of rear-facing chevrons in other countries. This followed after the inverted-V chevron design was combined with the new harlequin block markings on police vehicles. The UK was the first country to standardise a high-visibility marking scheme following the research undertaken by the Home Office to meet the following list of parameters for the Police (High Conspicuity Livery for Police Vehicles – Point 1.1.1 on p1)              

The specification required that a police patrol car operating on a dual carriageway or motorway should be:             

• Visible throughout the day and night and capable of being seen from a minimum viewing distance of 500 metres from on-coming road users; and
• Clearly recognisable as a police car
• The 500 metres minimum distance condition should apply during daylight hours in rain, mist, etc., though not necessarily in heavy rain or fog.
• Minimum illumination at night was defined as being that which is provided by an approaching vehicle with headlights set at the normal dipped position. This criterion applies without the roof lighting in operation on the police vehicle, since it is possible that this equipment can fail.

  

Full Battenburg Police Car with rear chevrons

 

          

The full Battenburg block colour of fluorescent yellow-green with the contrasting reflective blue blocks were (by good fortune) an ideal match to the traditional blue colour indicative of British policing blue that had been in use for many years. The blue blocks are used in opposition to the fluorescent yellow-green blocks because the contrasting blue remains the last colour to be seen [as a colour] before human vision switches to monochrome viewing (shades of grey) in darkness or under low light conditions. This contrast is one of the Battenburg advantages when viewed at at night. Chevrons do not share this advantage as they are red and yellow and even less if so the stripes are too narrow.               

Full Battenburg livery showing block contrast in low light

 

What colours were chosen for other UK emergency services? The police blue (the most visually effective opposition colour) had already been taken and the colour could not be copied by the other agencies. Sometime after Battenburg was trialled on Police vehicles, the ambulance and fire services subsequently chose red and green blocks to pair with the fluorescent yellow-green blocks on their vehicle designs. Neither the red or green reflective colour scheme is as visually effective as the blue colour under low light conditions. In addition, the full Battenburg layout that had been designed for passenger sedan vehicles was now adapted to the much larger slab-sided ambulances and fire trucks and this changed its performance parameters. When used off the motorways the Full Battenburg pattern is less effective amid the visual clutter of town and city landscapes, hence the half-Battenburg layout was created (Point 1.2.2.c on p6 of the report)          

The half-Battenburg design was introduced for use on general police vehicles not used for motorway duty and the chevrons were retained. (Point 1.2.1. on p5 of the report).         

• The emphasis is on ease of recognition as a police vehicle to increase awareness among the public of the fact that police resources are present, thereby providing reassurance and a deterrent against crime; and
• Outright visibility is of lower importance since vehicles will generally be seen at close quarters by pedestrians and road users travelling comparatively slowly.
• It was suggested that the likely maximum viewing distance would be closer to 200m.

Part 1 of this series explained that red & white chevrons were already in use on some British Police cars. This was an early attempt to reduce rear end collisions during police operations using pre-existing chevron designs. There are no additional scientific research sources referenced in any of the Battenburg documents. When the Battenburg researchers designed the block layout for the vehicle sides they considered rear chevrons to be a necessary element of the total layout. Chevrons were included as an attempt to moderate the risk of rear collisions. The rear chevron pattern never underwent independent testing away from of the side block pattern. Both the block and chevron patterns were always tested together as one unified marking scheme. The limited testing done on Battenburg was undertaken with a high level of emphasis on recognition of the Police corporate branding rather than visibility. The results acknowledge that Battenburg is a recognition livery that also includes high-visibility and conspicuity elements.            

The development of the half-Battenburg scheme and the researcher’s notes show the design team conceded that in a visually cluttered environment the full Battenburg begins to transition toward a camouflage effect. When full-Battenburg is used on ambulance vehicles in the UK the major element of visibility and conspicuity is the base vehicle colour (RAL 1016 fluorescent yellow-green). The Full-Battenburg design as the recognition element is sublimated to the full body coverage of the bright yellow paint. On fire trucks the Full-Battenburg blocks in red tend to bleed into the red body colour along the sides.           

The best colour for the rear chevrons was selected by the Battenburg research team based on the availability of fluorescent retro-reflective materials and current practise in the early 1990′s. In general the most recognisable colours used for chevrons were yellow and red alternating stripes. It was expected that it would be difficult to use the traditional black & yellow as the black stripe has limited effectiveness at long range and under low light conditions. Research indicated to the development team that yellow was generally perceived as a warning colour and the second colour, red, aligned with the colour of tail lights on the rear of vehicles (and was thus recognised as a rear-facing colour). It was surmised that the red & yellow together would be even more effective when combined with the new reflective colour materials in fluorescent yellow green, red or orange.             

At this point it should be noted that chevron designs should never be used on the front or sides of vehicles as they have developed into  a standardised rear-facing recognition pattern on vehicles!              

There were many different colour chevrons in the US up to the release of the FEMA study in 2009. Some emergency agencies misunderstood and attempted to colour-match the chevrons to their corporate markings or adopted chevron patterns using blue stripes because the blue colour was already in use on the Battenburg side markings. Chevron stripes laid down in Engineer Grade yellow and red reflective material do not possess any fluorescence brightness factor and therefore they will be less effective day and night.           

The correct interpretation of chevrons by other drivers is based on a response learnt  over time. Experience tells drivers that in general, black & yellow chevrons or red & yellow stripes are a danger warning. As an example of the opposite, some ambulances were fitted with green & white chevrons; these included the green as a GO colour and therefore subconsciously confused the viewer. Both NFTA and FEMA have confirmed their preference for yellow & red, as does the original UK Battenburg specification. If you decide to use chevrons instead of a single panel of colour (see Part 3) on the rear of your vehicle then the markings should be yellow & red in colour. If there is an obvious visual clash of colours with your existing markings then consider using a panel of single fluorescent colour instead of fitting chevrons.             

If you have any comments or questions about the chevron blog posts please send them in. If you have not read Part 1 – here is the link             

Part 3 will be posted soon and includes:             

• Dazzle, confusion and camouflage
• Chevrons – Urban vs Rural
• Viewing distances
• Depth perception and rate of closure
• Text and chevrons
• Front, side and bumper chevrons
• Doors, hatches & lockers
• Scene blocking – inline and echelon parking
• Chevron coverage and cost

              

Emergency vehicle chevrons – the blog series Part 1

Chevrons have become the latest new look in safety markings on emergency vehicles. Regardless of whether you love chevrons or hate them, the inverted-V markings will be displayed on even more Police, Fire and Ambulance vehicles every day. The numbers will increase regardless of the results found in any investigative studies. Chevrons will continue to be fitted to vehicles and this will be due more to popularity than the presence of reliable research.

The key question: Is the use of chevrons effective and good practise?
Chevrons have been affixed to UK Police vehicles since the early 1990’s. They were officially adopted as an element of the Battenburg design which was researched and designed in the UK by The Home Office.  Most of the Battenburg research was focussed on the contrasting squares displayed along the vehicle sides – the extra yellow & red chevrons were then literally tacked onto the backend of the chequered design. After the UK Police adopted Battenburg, the markings were later embraced by the ambulance and some fire services in Britain. The last decade has seen selected emergency service agencies throughout the world slowly begin to introduce chevrons on their fleets. These posts will hopefully offer some clarity about chevrons and aid in making an informed choice about fitting them to fleet vehicles.  

In January 2009 the United States NFPA 1901 (National Fire Protection Association) voluntary standard recommended all new fire apparatus to have at least 50% of the rear of the truck covered with six-inch red/yellow alternating stripes in a chevron (inverted V) pattern. This initiative was introduced to increase visibility and reduce the number of rear end collisions with fire appliances. A flow-on effect to ambulances has taken place due to both publicity and the large number of joint Fire/EMS agencies across the country.  Later in August 2009 the Federal Emergency Management Agency (FEMA) released the Emergency Vehicle Visibility and Conspicuity Study which commented on chevrons, but the report did not directly support their use. There is now a cascade of current and new vehicles in the US being fitted with chevrons as a visual safety device. 

This five part series will present and discuss the following issues about chevron markings: 

Part 1  

• Origins and traditions of chevrons
• Different types
• Interpretation of the chevron pattern
• LBFTS accidents and chevrons
• Available research

 Part 2  

• Chevrons on current & future vehicle fleets
• Differing expectations of Police, Fire & Ambulance
• Current fleet markings with chevrons on different vehicle styles
• Battenburg and chevron markings
• Chevron colour

Part 3  

• Dazzle, confusion and camouflage
• Chevrons – Urban vs Rural
• Viewing distances
• Depth perception and rate of closure
• Text over chevrons
• Front, side and bumper chevrons
• Doors, hatches & lockers
• Scene blocking – inline and echelon parking
• Chevron coverage and cost

Part 4  

• NFPA and FEMA recommendations
• Chevron stripe widths, number and angle
• Full or half coverage
• Reflective Materials
• Chevron colours

Part 5  

• Case studies
• Additional studies and research
• Reference material

Chevrons – Part 1  

The chevron pattern occurs in nature, generally as camouflage markings on fish or seen in the migratory formations of birds. Humans began to draw chevrons as decorative patterns in early art such as cave drawings and pottery. The patterns were later adapted for use in heraldic crests and shields. Modern day usage includes military and civil insignia, corporate logos, road signs and distance markings. Many different chevron designs have been displayed over the years as safety patterns on vehicles and this usage has increased dramatically over the last forty years. 

The V shape of chevrons can be aligned in any direction and each orientation has a different meaning depending on the intended message. On highway, traffic and vehicle signage  the chevron can have multiple meanings. Painted as markings on the road chevrons are used to time the safe distance between vehicles. Chevrons have been, and still are, used to delineate curves, corners, intersections and obstructions as warning signs on the roadside. Chevrons used for early road signs were coloured black on a yellow background. While the red/yellow colours are now the most popular colour combination, chevrons can be displayed in many other colours although these may not be as effective as the red/yellow pairing. Queensland Transport in Australia has printed A Guide to Hazard Markers showing how to interpret the chevron pattern displayed in different shapes, sizes and orientations.

The problems of correct interpretation with the chevron design have been outlined in the previous paragraph.  Considerable discussion has taken place over the last few years on two notable issues: First,the chevron patterns used on emergency vehicles show that traffic can pass on either side of the emergency vehicle; but this may not be the case at an accident scene or when the vehicle is positioned in the blocking mode. Second, chevron designs have typically marked fixed road obstructions using a sign that does not move around – now the chevron pattern is being transferred  to moving vehicles that can also stop still in the middle of  the road. This change of methodology appears to blur the very nature and impact of the original warning sign which every driver learns from day one!  

Looking at the first issue – the chevron design indicating it is safe to pass alongside; this may be a valid point if every driver knew the finer points of chevron layouts (see the link to the Hazard Marker Guide mentioned earlier). The reality is that most people don’t know and don’t recognise the individual variations. They will realise that the chevron is attached to an emergency vehicle and in general, drive reasonably according directions given at the incident scene in front of them. Some may not, but the chevron design probably won’t be the specific cause of this failure.  

The second point about displaying chevrons on moving vehicles is more ominous. Even though the pattern has been borrowed from stationary signage, emergency vehicles can be travelling at any speed, stopped in blocking mode or just parked at the roadside. Drivers will progressively learn that chevrons are no longer stationary, the design now hitching a ride on the back of vehicles. The danger here lies not in the transition from stationary sign to moving vehicle and then to a stopped vehicle, but in the probability that drivers may not realise that the emergency vehicle has in fact stopped, especially when parked in-line with traffic flow. This confusing effect is not limited to the chevron patterns, however chevrons are usually fitted to emergency vehicles in an effort to reduce or prevent rear-end collisions. The chevron pattern may reduce the ability of following drivers to judge closure rates - more on this point in later posts. 

Increasing rear-end safety was the prime reason for including chevrons in the Battenburg specification for vehicle markings. There are several interesting points to make about the chevron and Battenburg combination. Red & white chevrons had already been placed on UK police cars as an early response to an increasing number of rear-end collisions with police vehicles, especially on motorways. When the Battenburg livery was under development, the inverted V yellow and red pattern on the rear was added to the design. The research papers written about Battenburg make no reference to any separate testing of the chevrons, changes in the rear-end accident rate or reference to any other research indicating chevron effectiveness, just that the colour was selected for maximum conspicuity in-line with existing chevron road markings. 

Three well-respected researchers, Green, Hole and Langham, having written independent reports on physical and cognitive visibility stated that despite chevrons being fitted to British police cars,  the rate of rear-end collisions continued to rise. All three explain that the increasing accident rate is proof that physical conspicuity alone does not diminish accident rates. The fact is that cognitive functions play a large part as well. The two types of visibility are described by Langham as:   

• Physical Visibility – The most physically conspicuous objects possess the ability to capture the attention of the observer over and above other parts of the visual scene. Engel (1977) described physical conspicuity as the detection of a target in a brief presentation.
• Cognitive visibility  – Not only does an object such as a maintenance or works vehicle need to be ‘seen’, it needs to be ‘recognised’ for what it is – an increased risk and potential hazard. This is a concept known as cognitive conspicuity and relates to expectation in perception and can explain why, for example, a driver can look straight at a cyclist or motorcyclist and then drive straight into them….

Cognitive perception & information processing by drivers seems to play a major part in Looked but Failed to See accidents (LBFTS).  In his book The Psychology of Driving (p55), Graham Hole refers to the study An analysis of “looked but failed to see” accidents involving parked police cars (2002) undertaken by himself, Langham, Edwards & O’Neil. The study investigates LBFTS accidents involving other cars with police vehicles. The research found that many of the accidents occurred in good weather with a prolonged view of the stationary police car. The drivers were sober and the accidents occurred at no predictable time throughout the day.  

During follow-up photo simulations in the laboratory, police cars with side/rear markings and flashing warning lights were shown protruding onto the motorway and parked inline or at an angle to the traffic flow. These scenarios were then tested for driver response. The results showed that the vehicle parked at an angle to traffic encouraged a faster reaction time than the vehicle parked in-line with the traffic flow. When some participants in a second trial were distracted with a mobile phone task they either failed to respond to the hazard or had a virtual collision with the police car.  

These trials indicate five important points:  

• Highly conspicuous vehicles may not always be physically seen by drivers, especially if the driver is distracted.
• Drivers may see the conspicuous vehicle but then fail to process the information quickly or not at all, thereby narrowly missing or crashing into the police vehicle.
• Stationary vehicles parked in-line with the traffic flow may be seen, but if the vehicle pops up suddenly and is not expected then it may be perceived to be another moving vehicle until it is too late to stop and then a collision occurs. If the warning lights are flashing the viewer may also believe that active lighting indicates the vehicle is running to an incident and will not expect the police vehicle to be stopped on the road.  
• Emergency vehicles should be parked at an angle to the traffic flow so the unusual position clearly indicates to approaching drivers that a parked vehicle is ahead. The position of the car (either marked or unmarked) is usually an abnormal situation. This parking technique has been called echalon parking.
• Driving is often monotonous and drivers may not visually scan the changing conditions continuously, but at intervals. Periodic scans may not detect the radial expansion in the visual field of a parked emergency vehicle until it is too late.  If periodic scanning and fatigue are combined with a lack of expectation the combination may result in a collision. 

So where does this leave the chevron  position at the end of Part 1? Chevrons remain controversial with very little research or information available. The major experience with chevrons comes from the UK emergency services. Little follow-up research has been undertaken to assess chevrons or the Battenburg design. The UK Police study has shown that rear-end accident still occur after chevrons have been fitted to vehicles and when a driver is distracted the presence of lack of conspicuity markings makes little difference. There are still visibility studies relating to chevrons and they will be included within the next few posts. Please post any comments if you wish to raise a few issues or add some extra information.

Over the next week I hope to publish an extensive list of reference and associated documents relating to chevrons. Part 2 will be posted early next week and look at the following issues:

• Chevrons on current & future vehicle fleets
• Differing expectations of Police, Fire & Ambulance
• Current fleet markings with chevrons on different vehicle styles
• Battenburg and chevron markings
• Chevron colour

See you then!

Enhancing motorcycle conspicuity – emergency response & roadside.

Last week, I was at an intersection in Sydney waiting for a red light to change. Off to the left and without warning, a white blur appeared in the corner of my eye.  It took several seconds to recognize what was happening but by then the motorcycle had weaved its way across two-thirds of the intersection. The bike sped out of view; a blue masthead lamp mounted on the rear of the bike flashed – just once. The motorcycle rider, a Police Officer, was responding to an emergency call. There was no wail of the siren to be heard inside my car, no other timely warning; more important, there was no obvious indication that the bike was an emergency vehicle.        

Police motorcycles with Sillitoe markings

 

 The police motorcycle was engaged on a vital task; but painted bare white and travelling at high-speed it looked just like many other motorcycles found on the road (image at right). The blue chequered bands and the miniature police badges visually morphed into an indistinguishable blur. Small complex patterns can have the same effect – even turning some designs into camouflage (see image left below). Both the chequered and the miniature permutations of the Battenburg marking scheme are remarkably effective in breaking up the bike’s visual profile (especially when the bike is seen from the front). All this significantly increases the time taken by drivers to detect and recognise a motorcycle on response duty, thus reducing the valuable time they need to avoid the bike.                         

Police motorcycles - Battenburg markings

 

Furthermore, most motorcycles used by emergency services lack suitable mounting points for the warning lights; thus response motorcycles  tend to display only a minimal number of lamps – often just a single masthead lamp plus several other smaller lights facing the front and rear. The police rider on this particular day was wearing a fluorescent vest (enhancing his conspicuity) but this vest had no distinguishing markings and was again identical to the vests worn by scores of other ordinary bike riders.            

In simple terms, significant opportunities to moderate the risk to Emergency Service riders while simultaneously enhancing the conspicuity and recognition of the motorbikes are often overlooked. 

London Ambulance motorcycle in Fluorescent yellow/green

Compare the motorcycles described above with the London Ambulance Service (LAS) motorcycle in the photo at right. The LAS bike is painted one colour of yellow-green with retro-reflective fluorescent panels added to the body. The bike is visualised as a complete and recognisable object. The fluorescent panel markings “glow” in the light of dawn & dusk when thy are most needed. When the bike is seen from any angle the yellow-green colour clearly identifies the bike as an emergency response resource amongst other vehicles in traffic.  There is no need for identification patterns and the small NHS and LAS labels are all that is required.  
REMEMBER –  The series on <<<Chevrons>>> starts Tuesday 1 June 2010     

  

Chevron markings on Emergency Vehicles – the blog series

Have you ever wondered why inverted V chevron markings are appearing on emergency vehicles?  Is there any science behind the coloured patterns? These questions and many more will be answered in a series of blogs covering all facets of chevron markings; The series begins on Tuesday 1 June 2010. The posts will be published over 14 days in 5 episodes and the blog will be open for questions and comments. The series will discuss a range of factors including Chevron pros & cons, preferred layouts, chevrons & camouflage and the types of vehicles that should not use chevron markings + much more.  If you are considering rear-end protection, then this blog series should not be missed!         Here is the link to the series.   

Chevrons - All your questions answered

Lets clear up the confusion about reflectivity and vehicle waistlines!

The last few months have seen me answering  questions (more than a few times) about one of the recommendations listed as an opportunity in the FEMA Emergency vehicle visibility and conspicuity study. This one statement about reflective material has caused as much debate as the full report itself. The report advises: “Concentrate retro-reflective material lower on emergency vehicles to optimise interaction with approaching vehicles’ headlamps.” This is a simple piece of advice that recognises the sharp horizontal light cut-off found in the headlamps of modern vehicles. In basic terms; if you park a car at night so it is pointing at a wall a short distance away, then you will see that the lower part of the wall is brightly illuminated and the upper part of the wall is still relatively dark. The level of the cut-off line varies with the height and size of the vehicle, but not by much.                 

Headlamp cut-off displayed on wall

 

This sharply defined headlamp cut-off has serious implications for reflective signage mounted at a high levels above the roadway. This problem also affects large emergency vehicles like fire trucks and some taller ambulances. The companies that market reflective products have responded by developing new high-intensity (high reflectance) materials that use microprism technology to increase the level of reflected light. These improved materials are designed to compensate for the distinct light cut-off and operate more efficiently at lower illumination levels than the earlier beaded types.                      

So how does this affect emergency vehicles? Well, there have been many differing interpretations of how high up the vehicle the reflective stripes and markings should extend. The FEMA study covered all emergency services in the United States. As such, the vehicles used by Police, Fire and EMS agencies come in a great variety of shapes and sizes. The variations are endless; from Segway peoplemovers to sedans, van style ambulances to fire appliances and all the way up to truck/tractor-trailer combinations. The new trend towards lowering the level of reflective markings has begun to gain momentum.   

Fluorescent/reflective striping has begun to appear along the doorsill of a large number of emergency vehicles.  These low-level stripes are very effective when used in conjunction with an effective, wide, waistline stripe and additional contour stripes that follow the vehicle outline. The full vehicle waistline stripe is still the most important conspicuity component as it defines vehicle presence and length (thus overall size). The wheel arches may be cut out of the waistline stripe to further define size and vehicle orientation. Most important; the waistline stripe should be clearly visible when viewed through the windows of an average sized family car that is nearby or alongside. This helps the crew by providing maximum levels of emergency vehicle recognition for the surrounding drivers.                    

The emphasis of the FEMA report is directed towards larger emergency vehicles; that is vehicles bigger or taller than the average sedan. Ambulances, fire appliances and trucks from all agencies may find that reflective markings located above the 2 metre (6 foot) level are no longer illuminated effectively by car headlamps at short-range. Any major waistline stripe should be at least 200mm/8 inches wide and affixed on the vehicle no higher than 2 metres/6 feet from the ground. It is crucial that the reflective/fluorescent waistline stripe can be seen and recognised in daylight or darkness. The reflective coverage may extend from the door sills up to the waistline  as a lower-body panel of day/night colour if required. Any thin narrow waistline stripe is almost useless and does not enhance safety. To help compensate for low head light illumination at the upper levels of the vehicle, try switching to high-intensity prismatic products for markings. This will maximise reflection from the small amounts of light available above the headlamp cut-off.  

ACT Ambulance displaying reflective waistline, door-sill stripe and contour markings

I hope these notes help to settle the debate!