Why Pedestrians (And Bicyclists) Die. And What To Do About It.
Marc GreenAbstract While vehicle occupant fatalities have fallen steadily over the last decade, pedestrian deaths have remained constant despite attempts at remediation. This failure is rooted in lack of attention to the actual causes of vehicle-pedestrian collisions. These causes are evident in three types of research. One examines police reports and accident data to determine fault attribution. A second goes further by specifying the actual events that caused the collisions. The third, and most detailed method, is a case-by-case human factors analysis of documents, pictorial evidence and the collision scene itself. All three methods arrive at the same conclusion: the primary cause of pedestrian collisions is pedestrian behavior. Death rates have not fallen because attention has focused the burden of remedial measures exclusively on the wrong party - the driver. Instead, preventative steps would be more productively and more fairly aimed at changing pedestrian behavior. Lastly, the early evidence on bicyclist fatalities shows similar trends and leads to similar conclusions. Background
"The excessive speed of automobiles costs the lives of many persons; and that scarcely a week, sometimes scarcely a day passes without chronicling from one to a dozen deaths occasioned by the reckless driving of these machines. Fortunately, the chauffeur and his guests are the usual sufferers, and in their misfortunes as lawbreakers, the general public do not much concern themselves. Our sympathies are rather reserved for…the bystander who is run down and crushed by the enormous weight of these engines." -H. B. Brown, 1908. The status of the automobile. Yale Law Journal 17, 223-231.Pedestrian safety is receiving increased attention. The fatality rate of drivers and their passengers has declined over the last decade while pedestrian fatalities have remained constant . They constitute an increasing percentage of overall road deaths, so authorities are focusing more than ever on means to reduce the number. The failure to reduce pedestrian fatalities shows that previous strategies have reached a limit. The obvious question is "Why?" The short answer is that too much attention has focused on outcome to the exclusion of causation. An understanding of what actually causes vehicle-pedestrian collisions is an important precursor to improved safety. The reasons for failure to seek solutions in the real causes lie in Brown's quote, which expresses an ideology that focuses solely on outcome. Pedestrians (and bicyclists) are "vulnerable road users" (VRU's). The term evokes images of the weak and the defenseless in a David vs. Goliath confrontation where David is bound to lose. In this story, cars and drivers are, of course, the Philistines. The scientific literature and detailed collision investigation, however, tell a very different story. Moreover, I have performed in well over a hundred vehicle-pedestrian collisions during the last eighteen years. These investigations examined police reports and accident reconstructions, witness and participant statements, and photographic and video evidence. Moreover, they generally included first-hand scene inspections with time, space and lighting measurements, sometimes made during collision re-enactments. Analysis 1. Fault Attribution Research Police reports attribute greater blame to pedestrians than to drivers [e.g. 3], perhaps because pedestrians commit over 3.5 times more road violations . Other research has similarly confirmed that pedestrians are the prime collision cause, putting their fault at 75 percent, , 80 percent  and even 90 percent . The remaining cases were due to the driver or shared responsibility. For example, more recent research  found 59 percent pedestrian compared to 32 percent driver fault with the rest shared. However, fault attribution changes somewhat with circumstances. Police blamed pedestrians more for midblock collisions and cases where the pedestrian darted out at an intersection [e.g. 10]. Drivers received more blame during turns, especially to the left. This is expected since left turns create a high driver workload and tax attention . Drivers are very seldom the collision cause when traveling straight. Conversely, pedestrians gain more blame in low illumination , presumably in recognition that drivers cannot see as well in dim light. As discussed below, this is primarily due to pedestrian clothing choice. There are fewer data for vehicle-bicycle collisions, but the pattern is the same. Bicyclists are faulted in 50 percent of cases compared to 28 percent for drivers, with the remaining cases shared or uncertain fault . 2. Causes From Accident Data Other research has sought to identify causal factors. In most cases, the cause is some form of pedestrian behavior. Collision avoidance has two main mental components, detection and prediction. The road user must first detect the other party. The main factors in detection are visibility, which is determined largely by contrast, and conspicuity, which is determined largely by expectation. The road user must also be able to predict the present and future location of the other party. The present location is important because attention is limited, and drivers must know where to look. The future is important so the driver can gain situational awareness, i.e., determine what will happen if he maintains current course and speed. Pedestrians frequently confound driver detection and prediction. Ironically, pedestrians exhibit many of the behaviors used to fault drivers: lack of attention, using a phone or other distraction, failure to search, and even speeding (darting into the roadway) and perhaps most notably, drunkenness. Pedestrians cross illegally. Most road collisions occur when an "active" party intrudes on the right-of-way of a "reactive" party. In most collisions, the pedestrian is the active party. Pedestrians routinely ignore traffic rules, so illegal crossing is a major cause of pedestrian collisions, with some calling it the major cause [e.g. 12]. The numbers vary from study to study, but the lawlessness of pedestrians is well documented. Typical results include 80-93 percent of pedestrian fatalities occurred outside of marked crosswalks , 80 percent of pedestrians in fatal collisions had violated some law  and close examination of 40 collisions found unsafe pedestrian behavior in almost all cases . The general finding is that pedestrians tend to cross the road when it serves their goals of convenience and saving time, and they are not greatly concerned with potential safety implications . In sum, "Pedestrians often consider themselves outside the law" . Bicyclists are even greater scofflaws. They routinely ignore traffic controls . Failing to come to a stop at STOP signs is especially common. At low speeds, 80 percent do not stop while 34 percent don't even bother to slow . Further, 70-75 percent of bicyclists ignore red lights while 40 percent travel the wrong way down traffic lanes . When they do stop, it is usually only because heavy traffic leaves them no choice . They also feel free to switch back and forth between being vehicles (in the roadway) and pedestrians (on the sidewalk) as a means of avoiding having to stop at intersections. Bicyclist rule violations are probably more dangerous pedestrian illegal behavior. The bicycles' greater speeds leave less time for drivers to react. They also pose a small threat to pedestrians in general, but a large threat to older pedestrians. The law violation is a major cause of vehicle-bicycle collisions. A large proportion of collisions occur when the bicycle is traveling inconsistently with normal traffic flow, generally an illegal direction . Such behavior is highly dangerous because of the reduced detectability of small, low probability objects in unexpected locations. The purpose of traffic laws is to allow road users to anticipate each other's actions. Since perception depends heavily on expectation, the best way for pedestrians and bicyclists to be safe is to be in a place and at a time that drivers expect them. Of course, the same applies to drivers. Despite all this, some bicycle advocates encourage even more rule violation. They endorse red light and STOP sign running as a way to avoid vehicle exhaust behavior , but the real reason is probably that they don't want the work and inconvenience of having to slow or to stop. Many bicyclists apparently believe that they should be able to ignore traffic controls at their own discretion, which is a dangerous precedent. There is even now a push in some states for legislation to allow bicyclists to run STOP signs. This is sure to be a legal nightmare by removing any protection that drivers have from misbehaving bicyclists. Pedestrians dart into the roadway. Pedestrians also frequently suddenly run into the roadway, sometimes from behind an obstacle. For example, one study  found that 44 percent of pedestrian crashes were due to midblock dart-outs or dashing out at intersections compared to seven percent caused by a driver failing to see the pedestrian. Another observational study  found that pedestrians darted into the roadway from behind obstructing vehicles or buildings in 46 percent of near misses. However, other research  put "running into road" at only fifteen percent. All agree, however, that midblock-dart outs are a particular problem in child collisions, accounting for as much as 69 percent of injuries [see 2]. Another large study  classified 2100 vehicle-pedestrian collisions and divided them into six classes. Dart outs accounted for 42 percent [c.f., 23]. Most of the six scenarios have one thing in common: a pedestrian's sudden appearance and fast movement created a situation where the driver had little distance/time to respond. In other scenarios, physical constraints such as low lighting, background clutter, obstructions, bad weather, etc. further limited driver ability to respond. The only major scenario where pedestrian behavior was not a large factor occurred during a turn, where task demands tax the driver's limited attentional capacity. There is no mention of drivers on a straight path failing to yield as a major collision cause. Pedestrians are unpredictable. Collision avoidance depends on two factors, detection and prediction. In addition to darting, pedestrians often behave unpredictably by sudden changes in speed while crossing, often without searching for traffic . The variation in speed as well as in trajectory makes driver prediction of their future location difficult. Bicyclist turns are also difficult to predict . Although required by law, few bicyclists signal turns and passing. Pedestrians don't check for traffic. Pedestrian failure to search for approaching traffic is frequently cited [e.g., 24] as a major cause of collision and in some cases [cited in 16] as the major cause. Studies generally find that pedestrians don't look in both directions or don't look at all before crossing. Recent data , for example, put pedestrian "failed to look properly" as a factor in 48 percent of crashes. They are sometimes overconfident or distracted. Search failure is a common explanation for increased collision rate, even in crosswalks More specifically, pedestrians tend to move their head to search for traffic as they approach the curb but then reduce head movements once the curb is reached . The likely interpretation is that pedestrians make their decision to cross before reaching the curb and cease looking for traffic once the decision is made because they assume crossing is safe, - an example of confirmation bias. This explanation is supported by increased pedestrian search in riskier situations. For example, pedestrians search more for traffic when crossing during the "Don't Walk" phase of a crossing signal, but do not search during the "Walk" phase . Pedestrians are drunk. Pedestrian drunkenness, along with the use of other drugs, is a major factor in pedestrian collisions. Studies routinely find that anywhere from a third to as many as a half or more of pedestrians killed in road accidents were intoxicated at or above the .08 BAC level that is illegal for driving. Table 1 shows some of the results. The NTSB and earlier data suggest that the drunken pedestrian fatality rate has remained constant over the years
Table 1 BAC of pedestrian and cyclist roadway fatalities. See  for complete references. The reality is even worse than Table 1 suggests. Children and older pedestrians are seldom intoxicated, so the rate for non-senior adults is even higher than the table suggests. For example, the NTSB's 35 percent for the entire population increases to near fifty percent for pedestrians aged 35-44. Since fewer females are intoxicated, the rate for adult males must be extremely high. One study found that 70 percent of adult male pedestrian fatalities were intoxicated. Data on bicyclists are sparser, but alcohol also plays a major role in their crashes. Eichelberger et al (2017) found that the percentage of bicyclist fatalities oscillated between 20 to 30 percent over the 1982 to 2014 When most think of alcohol involvement in a crash, they usually assume that the alcohol was in the driver. NHTSA likes to promote this misconception with the deceptive "alcohol related" crash statistic. In fact, NHTSA data show that a collision between a drunken pedestrian and a sober driver is three times more likely than between a drunken driver and sober pedestrian (24 vs. 8 percent). A particularly thorough study  examined five years of pedestrian fatality data in London, UK and found that alcohol in the "driver/rider" was "only" a factor in 2.5 percent. Note that the driver was not necessarily intoxicated or the cause in all these cases. Amazingly, these data receive virtually no media attention. There is MADD, but no MOPP (Mothers Opposing Polluted Pedestrians). This is unfortunate because drunken walking (and possibly bicycling) is more dangerous than drunken driving. Pedestrians are overly confident. In most vehicle-pedestrian collisions, the pedestrian sees the vehicle approaching . This begs the question of why the collision still occurs. One answer lies in the repeated finding that pedestrians drastically overestimate their visibility to oncoming drivers at night [e.g. 31]. They believe that because the approaching vehicle is easy to see, the vehicle driver can see them. Pedestrians often simply walk in front of the approaching vehicle and assume that the driver will stop. Bicyclists also exhibit a similar overconfidence in their visibility at night [e.g. 32]. Overconfidence may lead to accepting risky gaps. Pedestrians and bicyclists, for example, often leave very small margins for error, 1-2 seconds . Pedestrians choose to make themselves invisible. Many pedestrian collisions occur at night, with risk increasing by a factor of seven . In 87 percent of nighttime collisions, the driver either saw the pedestrian only at the last split second or never saw the pedestrian. This is partly due to geometry, since a pedestrian emerges from the side, outside the headlamp beams and in the driver's peripheral vision . However, the lack of nighttime visibility is also due to pedestrian clothing. Visual detection depends on contrast, the difference in reflectance between an object and its background, which is dark at night. Many [e.g., 35] have shown that visibility distances to pedestrians wearing dark clothing is often too short for normal younger and especially older drivers to avoid collision on typical roads. A good rule of thumb is that recognition distance for a dark pedestrian is only a hundred feet [e.g., 36], but a police officer has testified that forty feet is more realistic. Moreover, virtually all studies show that some younger and many older attentive and alerted drivers completely fail to see unexpected pedestrians in dark clothing. Pedestrian clothing choice makes a great difference in detectability. Winter clothing has an average reflectance of only 5-6 percent, i.e., essentially black . White clothing can increase visibility distance by 470 percent . The use of "biological motion", attaching retroreflectors to joints so that the human form stands out from the background, is even more effective. I have made many nighttime pedestrian light measurements and can confirm that clothing choice is often the major difference between life and death, exceeding even road lighting in importance. Still, pedestrians fail to appreciate the beneficial effects of clothing reflectance and "biological motion" [e.g. 31]. Bicyclists would also benefit greatly from clothing that is more conspicuous. Bicycle lights are a step in the right direction, but they are not very conspicuous by day and camouflaged by urban background clutter at night. In contrast, a large-scale study  of 6,800 bicyclists found that visibility clothing decreased bicyclist collision rates by more than 70 percent. In sum, dark clothing and invisibility is a choice. Whether it is due to fashion or to avoid dirty clothing, it is still a choice that the VRU can easily change. The driver who is put in a difficult position by having to detect and recognize a dark object at night has no choice. Pedestrians are distracted. While there is enormous research on distracted drivers, the problem of distracted pedestrians is only now beginning to receive attention. Studies have found that about 30-47 percent [38, 39] of pedestrians crossing the street are distracted. Cell phone conversations and texting were by far the major detractors. The problem is certain to grow due to the dramatic increase of cell phones for a variety of increasingly attention-absorbing tasks. Distracted pedestrians exhibit the same impairments as distracted drivers. Table 2 shows some of the impairments just for merely talking on a cell phone while crossing.
Table 2 Cell phone distraction and representative references. See  for complete references. Pedestrians engrossed with their smart phones exhibit the same deficits but to an even higher degree. As with drivers, texting and emailing are the perfect storm of distraction - intense foveal concentration to a small display requiring good acuity while performing a task that requires deep cognitive processing for an extended time. Sooner or later, looking away from where you are going leads to trouble. This is as true for pedestrians as it is for drivers. The growth of dangers posed by such distraction can only increase from here. I saw no technology-distracted pedestrian collisions ten years ago. A few began appearing about five years ago, most involved listening to music or a cell phone conversation. Now they are common, primarily pedestrians looking at their smart phones. In one recent case, the pedestrian reading a text message was also crossing against a red light. She never looked up or noticed the bus traveling only 15-20 mph that collided with her. In another, a pedestrian reading his email wandered into an intersection, stopped and was struck by a car. Similar distraction effects have been found in cell phone using bicyclists, who exhibit even more unsafe behavior . When using a cell phone, they engaged in more risky behavior and more often forced a vehicle driver to perform an avoidance response . Pedestrians walk with their backs to traffic. While most collisions occur during crossings, many happen when pedestrians walk in the road. In most jurisdictions, the law requires pedestrians to walk facing traffic when they are in the roadway because it is far safer. It is easier to see a vehicle approach from the front than to see it by occasionally looking over the shoulder. Drivers are better able to see faces than the dark backs of pedestrians. This is why pedestrians facing traffic have 77 percent fewer collisions . When collisions do occur, moreover, pedestrians facing traffic suffer milder injuries. Pedestrians facing traffic also choose larger and safer gaps, possibly because they are a population of lower risk takers. Again, the published data are consistent with my investigation experience. In several collisions, pedestrians (often multiple pedestrians strung out across the roadway) walked with their backs toward traffic. No cases had a pedestrian walking toward the vehicle. When a collision occurred late at night, the pedestrian walking in the road was almost invariably drunk and often on drugs. Pedestrians don't know the traffic rules. A large percentage of pedestrians have an incorrect understanding of when an approaching vehicle is required to stop for them. A questionnaire study  of attitudes found that both pedestrians and cyclists are prone to self-serving interpretations of safety and responsibility, especially for nighttime conditions. 3. Detailed Human Factors Collision Investigation These research data match the analyses of over 100 detailed collision investigations. The pedestrian behavior described above caused almost all collisions. The most common collision scenario occurred when the pedestrian violated driver expectation, especially in low visibility where safety margins shrink. In these cases, the pedestrian had usually violated the driver's right-of-way by ignoring a red traffic signal or crossing midblock. Sometimes they walked in the wrong direction in the roadway. Collisions due to the erratic pedestrians absorbed in their smart phones are increasingly common. Driver behavior was seldom the primary cause. For example, I have seen numerous cases of pedestrians crossing illegally, but only four cases where a vehicle collided with a pedestrian in a marked crosswalk. Two cases occurred in the nighttime at intersections where the streetlamp was burned out and visibility was a significant factor. One of these was a left turn and the other had a driver with BAC=.12. The two other collisions occurred when a car in the near lane stopped to allow a pedestrian to cross. As the pedestrian began walking, a vehicle in the center lane approached. The stopped car blocked the sightline between the pedestrian and the center lane driver, so both continued to the collision. The scenario is so common that it has its own name, "multiple threat". Limited visibility, not driver behavior, was the primary cause. DISCUSSION 1. What About Drivers? The discussion has drawn a heavily one-sided view of collisions, painting pedestrians as the primary authors of their own misfortune. There is good reason. First, it is an "inconvenient truth" that pedestrian behavior is the primary cause of the collisions. Second, the bias against vehicles is so strong that it is hardly news to say that drivers sometimes cause pedestrian fatalities. Feeding the anti-car confirmation bias is unproductive. Many already apparently believe that it is the driver's responsibility to perfectly compensate for even the riskiest pedestrian and bicyclist behavior. In the case mentioned above, the pedestrian who was sending a text was also crossing against a red light. The driver's attention had been diverted by yet a second illegal pedestrian running midblock across the road. The driver was still criminally charged. In another case, a driver spent three years in jail for colliding with a .24 BAC pedestrian who wandered into the middle of the road. Certainly, the driver controls greater energy and the pedestrian suffers the greater consequences. That does not necessarily make the driver responsible for the collision. Examination of human factors shows that the driver may control the energy, but the pedestrian has greater control over whether a collision will occur:
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