World Day of Remembrance – United Nations Designated
The World Day of Remembrance For Road Traffic Victims has been designated as the third Sunday in November of each year. https://worlddayofremembrance.org/
Moving Queues of Stopped Traffic – A Safety Challenge on Major Expressways
Difficulties arise when drivers expecting the free flow traffic on the right, experience the stopped traffic on the left.
Moving queues of stopped traffic on major expressways are a serious problem for public safety. Drivers who may travel for several hours at speeds of over 100 km/h develop the expectation that this free flow will continue into the immediate future. Maintaining a vigilance over several hours toward a seemingly unchanging condition may be performed by many drivers over many instances. However the high frequency of exposure over a life-time of driving means that eventually instances of inattention will occur. Of the thousands of drivers that travel on a segment of a major expressway every hour it only requires the inattention of a single driver to cause a major incident. This is particularly so when an unexpected incident causes a sudden stoppage of traffic and a queue begins to snake its way backwards towards approaching drivers who are not expecting that stoppage.
Lack of formal training in human behaviour causes many judgments to be made and misconceptions to be developed that fail to address the root problem. Those who could provide that insight are often not those posting their views on social media or given an opportunity to inform the public in formal news segments. Attention failures are not indicators of driver “stupidity” but are a demonstration of the reality that human performance has certain limitations because of the way we process information and respond to it. Though it is insufficient in its detail, it can be said that humans focus their attention on one item of information at a time and we are programmed to focus our attention on items that are seemingly of greater importance. Thus in most traffic instances, it is not that drivers are inattentive but rather they are attentive to other things besides what we, in hindsight, expect of them.
It is not that distant in time when similar problems of human behaviour have caused injuries and fatalities in various farm and industrial settings. Various stamping, crushing and cutting machines have been operated by humans who have sometimes become entangled in the machinery resulting their being stamped, crushed or cut apart. The obvious comment could be made that these operators simply had to stop placing their hands or clothing into the location of the machinery that would cause them to be entrapped and dragged into the moving machine. Such sage advice did not solve the problem. Instead various guards were put in place so that operators would not be placed in proximity to mechanisms that would capture them. Also various sensors were built into the machinery that would stop the operation of the machinery if an entrapment of the operator was sensed. This was the progress of technology that corrected the safety problems. While great effort may be expended via public education to the need to maintain vigilance on major expressways it is unlikely to make a large difference in increasing public safety. As in the past technological changes are needed.
One technology that could make a large difference is automatic emergency braking. Such systems do not require the driver to be attentive to traffic ahead in order to apply braking because the system is designed to detect stopped or slowing traffic that may not be in the driver’s view. Time is required before the such systems improve in their ability to deal with the full complexity of all real-life scenarios.
In the meantime some transportation agencies have attempted to develop technological systems on the highways themselves. As an example in 2011 the Texas Department of Transportation (TxDOT) developed a system of early warnings for queues of stopped traffic on approach to expressway construction sites. Portable speed sensors were erected to detect the speed of traffic as far back as 7.5 miles from the construction zone. Portable, changeable message signs were erected to warn drivers of the developing stoppage of traffic. Also portable rumble strips were laid across the lanes to create audible and tactile warnings. TxDOT indicated that their system reduced crashes by 45%. Such systems may not be a full solution for situations where a sudden stoppage occurs from emergency situations such as collisions. However they are an attempt in the proper direction of using technology to correct a serious, recurring safety problem that exists throughout modern expressways.
In the immediate area of southern Ontario, expressways such as Highways 400, 401, 402 and 403 carry a large percentage of heavy truck traffic. It is not uncommon to see trucks travelling very close to each other at highway speeds. As shown in the photo below, the view of these drivers is blocked by the wall created by the large dimensions of the trailers of the trucks ahead. Thus they are unable to detect the occurrence of emergencies that develop.
Truck drivers have limited visibility ahead when travelling too close together and are unable to react to situations such as merging traffic from an on-ramp.
There is various research on heavy truck braking. One source comes from the U.S. Federal Highway Administration as shown below.
The table shown the next two photos provides data on the braking distances required by various heavy trucks from highway speeds.
The reported distances (in feet) do not include the perception-response delay that would occur as the driver detects, identifies and then commences a reaction to the incident. In some instances, such as a bob-tail (a road tractor minus its trailer), the braking distance can be over 500 feet or 150 metres. This is about the length of 1 and a half football fields.
There should be little wonder when, faced with a sudden requirement to brake such truck drivers are often the ones who collide into lighter, stopped vehicles ahead. Rather than singling these persons out as the cause of the highway problem, it is necessary to recognize the difference in exposure and address the root of the problem.
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Increased percentages of heavy truck traffic is also a problem because of the inability to brake at the same level of efficiency as light vehicles.
Perception Response is a Big Deal in Accident Reconstruction
Observing how drivers react to the green traffic signal is a useful tool in accident reconstruction.
How drivers perceive and react to traffic events is an important issue. In the North American judicial systems it can mean whether you are charged with a criminal offense, pay large amounts in a civil claim, or are denied compensation for a catastrophic injury.
Many research studies have been published over the years and these have been used by expert witnesses at trial to claim one thing or another with respect to someone’s actions. It is not too uncommon for the timing of these actions to be critical in determining to the court whether someone is convicted of a crime or faces some monetary penalty in civil proceedings. The arguments at trial can be broken down to fractions of a second as experts claim that a certain scenario is supported by a certain body of research.
At Gorski Consulting we chose to collect our own data rather than relying solely on the reported research of others. A common source of perception-response data comes from video-taped observations of the reactions of drivers to a changing traffic signal, as shown in the example photo above.
In a typical urban environment there are often two through lanes and a left turn lane that may be occupied by vehicles in each lane. How drivers react to the changing of a red signal to green is an interesting source of research data. The table below shows the results from 24 observations of drivers’ reactions while stopped for a red traffic signal in the passing lane of a roadway. That driver would be the middle one shown in the above photo.
The data was obtained from examining the videotape and noting the timecode when the traffic signal turns green and then noting when the brake lights of the vehicle become extinguished.
Note that, on average, the delay was about 0.40 seconds. That is an unusually fast reaction.
In an oft quoted section of the book entitled “Forensic Aspects of Driver Perception and Response” authored by Professor Paul L. Olson he made the following observation (Page 187):
“Given a reasonably clear stimulus and a fairly straightforward situation, there are good data indicating that most drivers (i.e. about 85 to 95%) will respond by about 1.5 seconds after the first appearance of the object or condition of concern. The evidence also indicates that the minimum perception-response time for this straightforward situation is about 0.75 second. Thus the probable range of perception-response times for reasonably straightforward situations should be 0.75 to about 1.5 seconds. Please note these values are not chiseled in stone on tablets along with other commandments! The fact that an investigator may calculate that the perception-response time for a given individual under what is judged to be a straightforward situation is 1.6 seconds or even 1.7 seconds is not a basis for judging the driver’s behavior to be unreasonable.”
What would the experts, or anyone else say to the data shown in the above table? Does it contradict Dr. Olson? Even without discussing the differences in the data the first thing the observer should consider is the above-noted data is only reporting 24 observations and such a small sample could cause the true mean (statistical “Population Mean”) to reside to the left or right of this sample mean.
One would also need to consider the issue of “primed” reaction. In other words, the drivers stopped at the traffic signal will likely be aware that their reaction (release of the brake pedal) will be required in the very short future. They are also provided with other clues such as the condition of the traffic signal along the opposing roadway. If they are frequent users of the roadway they will become aware of the typical timing of the signal and when it is likely to turn green. Such pre-existing knowledge is what can cause drivers to react much quicker because the required reaction is not totally unexpected. Also the above drivers have only a single reaction to consider (release of brake) and they do not have to may a choice whether other reactions (steering, looking in a mirror, etc.) are required. Thus this decreases the delay in this simple reaction scenario.
Furthermore, note that in observation #12 the driver of a Honda Accord released the brake pedal 4.07 seconds before the traffic signal turned green. This has caused the standard deviation of the mean to be increased to 1.01 seconds and it has obviously affected the lowering of the average, reported mean.
This example demonstrates the importance of the critical evaluation of what has been reported to us. As receptors of information being provided by experts we must be vigilant to the details and be prepared to question conclusions even though they might come from someone who looks like they know something because of their credentials or experience.
Is Official Advice for Cyclist Versus Pedestrian Safety a Contradiction?
Facing traffic while walking on a paved shoulder is good advice – but do we give the opposite advice to cyclists?
The OPP provided some good advice to the public when submitting the above photo on their Twitter account. In the immediate duration before a crash every additional second is extremely important and can be the difference between a pedestrian successfully avoiding an errant vehicle or facing a possible deadly consequence. Facing traffic may give you that valuable additional second.
Despite this useful advice our society seems to provide the opposite advice for cyclists who face a similar jeopardy. Cyclists who may ride even closer to fast-speed traffic than pedestrians are forced to ride with their backs to that traffic. The danger has become so apparent in Toronto that cyclists have begun attaching horizontal pool noodles to the backs of their cycles.
The pool noddle in an interesting safety strategy but is unproven.
Why is it so is important to give pedestrians that extra second or two of reaction time but that is not considered important for cyclists who face collisions of similar severity without any meaningful protection? This is a societal question that begs an answer from those who continue to place cyclists in this dangerous environment.
Results From Bicyclist Observations on Trafalgar Multi-Use Path in London, Ontario
Residents were puzzled to observe the large number of tripods and video cameras positioned along the Trafalgar bike path on August 28, 2018 in London, Ontario.
August 28, 2018 was “Observation Day” for the Trafalgar Bike Path in east London, Ontario. This was the day that Gorski Consulting set-up 10 video cameras and documented the speeds of cyclists going up and down the slope from the north side of the new CN bridge to Trafalgar Road. The path had been previously marked at 25 metre intervals and the cameras were used to observe as cyclists passed the painted markers. Later analysis of the timecode of the synchronized cameras led to the calculation of the time that a bicycle travelled from one marker to the other. As an example if a cyclist took 3 seconds to travel the 25 metres from one marker to the next this meant that his average speed was 8.33 metres per second. By multiplying this value by 3.6 we transfer this into km/h, or 30 km/h.
View of a GoPro camera anchored to the railing of the CN bridge to document the speed of cyclists travelling up and down the slope of the path.It becomes a simple process to tally up the motions of each cyclist in a spreadsheet and this provides an indication of the variance in speeds with maximums and minimums.
The slope of the path needed to be determined and that was measured on a previous day.
View of video camera pointing southward up the slope of the bike path toward the CN bridge.
The table below shows the measurements of the slope of the path from the CN bridge to the terminus of the path at Trafalgar Road.
The observations of the cyclists on August 28, 2018 led to the creation of the table of speeds shown below.
The “Bridge to 10m” refers to the 10-metre section of the path at the north end of the CN bridge which is the portion shown in the second photo (above) in this article. The observation distances go as far as 175 metres north while the terminus of the path at Trafalgar Road is approximately 325 metres north of the CN Bridge. The observations of cyclist speeds could not be followed all the way to Trafalgar Road because it was impractical to stretch the camera positions over such a long distance. Rather it is expected that addition testing will be performed on another day to capture the cyclist motions for the remaining distance from 175 to 325 metres.
The purpose of this testing is to explore how a steep downslope can affect the speed of cyclists. In this case, northbound cyclists need to make a sharp left turn as they approach the Trafalgar underpass and we have previously mentioned how challenging that can be. Even though the steepest portion of the downslope is almost 300 metres away from that sharp left turn it still contributes to the elevated speeds as demonstrated by our coasting tests that were described in an earlier article. Even the Pottersburg Creek bridge, located just before Trafalgar Road contains a downslope of 5.8 % and this also contributes to the elevated speeds.
Above all, this is a research experiment. It is a safety lesson for those who need to consider how the characteristics of bike paths affect the public’s safety.
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