Conspicuity as a Factor in Motorcycle Accidents (Motorcycle Accident Reconstruction)

Researchers have sometimes proposed that when a passenger car driver violates the right-of-way of a motorcyclist, the motorcycle's inconspicuity is to blame (or is, at least, a contributing factor). In 1977, Hurt noted that “the most likely comment of an automobile driver involved in a traffic collision with a motorcycle is that he, or she, did not SEE the motorcycle…” (emphasis in original). Hurt continued: “The origin of this problem seems to be related to the element of conspicuity (or conspicuousness) of the motorcycle; in other words, how easy it is to see the motorcycle. When the motorcycle and the automobile are on collision paths, or when the vehicles are in opposing traffic, the conspicuity due to motion is very low, if it exists at all. Consequently, recognition of the motorcycle by the automobile driver will depend entirely upon the conspicuity due to contrast. If the approaching motorcycle and rider blend well with the background scene, and if the automobile driver has not developed improved visual search habits which include low-threat targets (such as motorcycles and bicycles, as contrasted with the high-threat targets presented by trucks and busses) the motorcycle will not be recognized as a vehicle and a traffic hazard exists.” Without discounting the factors listed by Hurt, it should also be recognized that his statements go too far, discount too much, and are not fully supported by later research. Though he acknowledges it elsewhere, physical obstructions from other traffic, inattention and distraction on the part of a passenger car driver, and lack of expectation to encounter a motorcycle are other factors that may account for a driver not seeing a motorcyclist.

As Bertrand and his colleagues noted in 2014, “much previous research has focused on motorcycle properties, such as size, shape, and color to explain its inconspicuousness…Much of the motorcycle safety research conducted since has focused on making motorcycles more conspicuous, generally through various lighting treatments such as headlight modulators, additional lights, and bright reflective garments…There is some debate, however, regarding the effectiveness of these measures…it has been suggested that the problem may not be one of conspicuity at all…collision statistics remain largely unchanged, suggesting that the issue may not be related solely to the motorcycle’s static properties” (emphasis added). Bertrand’s research suggests that the motorcycle and rider’s dynamic properties, such as lane position, also make a difference to the likelihood a motorcyclist will be detected.

Bertrand et al. used a driving simulator to examine the motorcyclist’s lane position as a factor in crashes where a passenger car driver turns left and violates the right of way of the motorcycle. He described their experiment as follows: “Seventeen participants faced oncoming traffic in a high-fidelity driving simulator and indicated when gaps were safe enough for them to turn left at an intersection. We manipulated the size of the gaps and the type of oncoming vehicle over 135 trials, with gap sizes varying from 3 to 5 s, and vehicles consisting of either a car, a motorcycle in the left-of-lane position, or a motorcycle in the right-of-lane position. Our results show that drivers are more likely to turn in front of an oncoming motorcycle when it travels in the left-of-lane position than when it travels in the right-of-lane position.” Bertrand and his colleagues had determined, based on the intersection geometry and the acceleration capabilities of the vehicle, that “a three-second gap in a stream of oncoming traffic would not allow for the safe execution of a left turn, that a four-second gap would allow for the safe execution of a left turn, but leave very little safety margin, and that a five-second or more gap in the stream of traffic would allow for the execution of a left turn and leave a reasonable safety margin.”

For each of the 3 gap sizes – 3 seconds, 4 seconds, and 5 seconds – participants chose to turn more frequently when the motorcyclist was in the left-of-lane position than when the motorcycle was approaching in the right-of-lane position. Bertrand concludes that, “these results are consistent with our hypothesis that the right-of-lane position offers more motion cues to an oncoming driver and is therefore more likely to deter oncoming drivers from crossing in front of a motorcyclist’s path as they approach an intersection. However, our findings are inconsistent with some motorcycle rider training which motorcyclists generally leave with the belief that they should always ride in the left portion of the lane. Our results suggest that the right-of-lane position may be a safer riding position when entering an intersection.”

Unfortunately, however, the crash scenario studied by Bertrand is not the only one likely to be encountered by motorcyclists. Drawing general conclusions about the optimum lane position for a motorcyclist who may be encountering multiple possible crash scenarios simultaneously seems unwarranted based on Bertrand’s research alone. There are scenarios a motorcyclist could encounter where their choice of lane position, and how it might or might not affect visibility and conspicuity, may compete with other crash avoidance factors. Ouellet [1990], for example, examined the optimal lane positioning for motorcyclists in terms of the time they had available for collision avoidance, noting that “lane positioning as the rider approaches a potentially threatening situation is a simpler, more reliable and more effective means of reducing collision risk than reliance on emergency braking.” His study revealed that “the motorcycle rider can do more to avoid a collision by moving laterally away from a threatening vehicle, putting at least one lane-width between them, before a vehicle begins to violate his right-of-way, than he can be effective braking after the other vehicle has begun to violate his right-of-way” (emphasis in original). Depending on the intersection geometry and what other vehicles are present, these statements could dictate a left-of-lane, right-of-lane, or center-of-lane positioning.

In 1989, Olson examined the literature related to why passenger car drivers sometimes fail to detect motorcyclists. Although he noted that “considered logically, it seems reasonable that motorcycles should be less conspicuous than cars because they are smaller,” Olson questions motorcycle conspicuity as the likely explanation for car drivers missing motorcycles. He observed that “the strongest support for the conspicuity hypothesis may be that the offending operator often reports a failure to detect the other vehicle.” However, Olson noted that “the conspicuity hypothesis has not been seriously challenged. Almost all investigators have accepted it as fact, concentrating their efforts on means to improve conspicuity rather than on asking whether the hypothesis is correct. This is unfortunate because alternative hypotheses can be advanced. Some have research data to support them; some are speculative. All are consistent with the known facts…” Olson noted that drivers claiming to have not seen another vehicle is not unique to motorcycle-car intersection collisions. He stated: “Violations of right of way are a common cause of collisions between automobiles, and afterward the errant driver often claims not to have seen the other vehicle. This should not be surprising. Of all the reasons that someone would deliberately move into the path of an oncoming vehicle, failure to detect it must be high on the list. But if the claimed failure to detect is not unique to motorcycle collisions, then it is not evidence for a special conspicuity problem with motorcycles.” Olson discussed other explanations for why passenger car drivers sometimes miss motorcyclists, including visual obstructions and errors in the drivers’ estimates of how far away a motorcycle is and how fast it is traveling.

In 1996, Hole, Tyrrell, and Langham reported three experiments related to motorcycle conspicuity. These experiments involved showing the test subjects a series of images containing traffic. Some of these images contained motorcycles and some of them did not. Less than half of the images contained motorcyclists, so that the test subjects could not assume there would be a motorcyclist in each image. Hole and his colleagues recorded the time it took the subjects to determine if a motorcyclist was present in each image. They varied if the motorcycle headlight was on or not, the type of clothing worn by the motorcyclists (plain dark, plain bright, patterned dark, and patterned bright), the distance of the motorcycles from the viewer, and the driving situation (urban or semi-rural). They also examined the influence of background clutter on the conspicuity of the motorcyclists. These researchers reported that “the effectiveness of the conspicuity aids used, especially clothing, may depend on the situation in which the motorcyclist was located: bright clothing and headlight use may not be infallible aids to conspicuity. Brightness contrast between the motorcyclist and the surroundings may be more important as a determinant of conspicuity than the motorcyclist’s brightness per se. Motorcyclists’ conspicuity is a more complex issue than has hitherto been acknowledged.”

A sampling of specific findings by these researchers included the fact that “motorcyclists were detected more quickly the nearer they were to the viewer, and in both locations the biggest difference between the headlight-off and headlight-on conditions was at the furthest viewing distance;” “the effectiveness of the headlight as a conspicuity aid was much less clear-cut in the urban setting than in the semi-rural environment…headlight use in the urban location enhanced conspicuity only when the motorcyclist was wearing plain bright or patterned dark clothing: when patterned-bright or plain dark clothing were worn, subjects responded faster when the headlight was off than when it was on. In the urban setting, a consistent advantage for headlight use was demonstrated only when the motorcyclist was wearing patterned-dark clothing;” “in both locations, many more motorcyclists were undetected at the furthest distance from the viewer than when the motorcyclist was nearby…for the semi-rural location, at all three distances, there error-rate for the slides in which the motorcyclist’s headlight was lit was half that for the slides in which the headlight was unlit…For the urban location, at all three distances, the error-rate for the slides in which the motorcyclist’s headlight was lit was lower than that for the slides in which the headlight was unlit, but not markedly so;” “in both locations, there was little effect of clothing type except possibly at the furthest distance.”

Hole, Tyrrell, and Langham noted several limitations of their study. Among these was their observation that “problems are also caused by the fact that instructing subjects to look for motorcyclists may cause them to process a traffic scene in ways that are different to those used in normal driving…Cole and Hughes (1984, 1990) distinguish between two types of conspicuity. ‘Attention conspicuity’ refers to the capacity of a stimulus to be noticed when the observer is not actively looking for it. ‘Search conspicuity’ refers to the capacity of a stimulus to be noticed when the observer is specifically looking for it. The experiments reported here have examined factors affecting motorcyclists’ search conspicuity, but in real life, attention conspicuity may also be important.” Finally, Hole, Tyrrell, and Langham observed that “the fact that there were few differences between conditions when the motorcyclist was nearby implies that motorcyclists’ conspicuity at the close range within which accidents often occur might be relatively unaffected by such factors: within this range, it is possible that the psychological state of the driver may play a more important role than the physical characteristics of the motorcyclist…inappropriate expectancies may be more important in accident causation than the motorcyclist’s physical properties.”

In 2010, Gershon reported two experiments related to motorcycle conspicuity. The first experiment “evaluated the influence of [the motorcycle and rider’s] attention conspicuity on the ability of un-alerted viewers to detect it.” The second experiment “evaluated the [motorcycle and rider’s] search conspicuity to alerted viewers.” Gershon and his colleagues varied the driving scenario (urban and inter-urban), the motorcycle rider’s outfit (black, white, and reflective) and the distance of the motorcycle from the viewer. In the first experiment, Sixty-six students were individually presented with a series of pictures. They were allowed to view each picture for 0.6 seconds and then were asked to report all of the vehicle types they observed in each picture. In the second experiment, 64 participants viewed the same pictures utilized in the previous experiment. In the second experiment, though, the participants were instructed to look for motorcycles and to report whether or not each photograph showed a motorcycle.

For the first experiment, Gershon reported that the detection of the motorcycles “depended on the interaction between its distance from the viewer, the driving scenario and [the] rider’s outfit…when the [motorcycle] was distant the different outfit conditions affected its’ attention conspicuity. In urban roads, where the background surrounding the [motorcycle and rider] was more complex and multi-colored, the reflective and white outfits increased its attention conspicuity compared to the black outfit condition. In contrast, in inter-urban roads, where the background was solely a bright sky, the black outfit provided an advantage for the [motorcycle’s] detectability.”

For the second experiment, Gershon reported that the “detection rate of the alerted viewers was very high and the average reaction time to identify the presence of a [motorcycle] was the shortest in the inter-urban environment. Similar to the results of experiment 1, in urban environments the reflective and white clothing provided an advantage to the detection of the [motorcycle and rider], while in the inter-urban environment the black outfit presented an advantage. Comparing the results of the two experiments revealed that at the farthest distance, the increased awareness in the search conspicuity detection rates were three times higher than in the attention conspicuity.” In other words, the rider’s clothing made a difference, but the driver’s awareness that there would be motorcyclists in some of the pictures (expectation) made a bigger difference. As Gershon noted, “unfortunately, detectability – especially attention conspicuity – is compromised by the perceptual characteristics of the environment that change continuously along a route. Thus, to increase detectability, [motorcycle] riders need to be aware of the perceptual aspects of their riding environment. In parallel, the results of the second experiment with alerted viewers demonstrate that other road users (e.g., car drivers) can improve their detection performance when they increase their level of expectancy and awareness concerning a possible existence of a [motorcycle] on the road (as drivers with high expectation obtained nearly 100% detection rates).”

That a lack of expectancy may play a significant role in passenger car drivers failing to recognize the presence of a motorcycle is consistent with the fact that motorcycles make up a relatively small percentage of the vehicle population, and therefore, may not be encountered that frequently by passenger car drivers. In 2015, motorcycles made up only 3 percent of all registered vehicles in the United States [NHTSA, 2017]. Layer on top of that weather that limits the riding season in many states and motorcycles end up accounting for only 0.6 percent of all vehicle miles traveled in the United States [NHTSA, 2017]. Thus, the typical passenger car driver will encounter motorcycles less frequently than they encounter other passenger cars. The lack of expectancy that this low frequency may cause is targeted by advertising campaigns in some states with slogans such as “Share the Road: Look Twice for Motorcyclists” [TxDOT, http://www.txdot.gov/inside-txdot/media-center/psas/motorcycles-bicycles/share-road.html].

Jenness, et al. reported a daytime field experiment to determine if the gap acceptance behavior of drivers turning left in front of a motorcycle changed with forward lighting added to a motorcycle above and beyond the standard low beam headlamp that turns on automatically [2011]. The intent of daytime running lights on motorcycles is to increase conspicuity, and thus, to overcome passenger car drivers’ lack of expectancy and increase the likelihood passenger car drivers will recognize the presence of motorcycles. In his 1977 study, Hurt had noted that “one important countermeasure is the use of a lighted motorcycle headlamp during daylight…The data collected by the USC-DOT Motorcycle Accident Research Teams shows that the motorcycles NOT using the headlamp-on during daylight are overrepresented in the accident population. The bouncing, flickering headlamp of the moving motorcycle is a powerful attention-getting mechanism, which greatly improves motorcycle conspicuity in traffic.” A study by Olson confirmed this finding, noting that “the most effective means of improving daytime conspicuity…is to require motorcyclists to drive during the day with their low-beam headlamp turned on” [1981].

The study by Jenness, et al. utilized 32 drivers (19 to 67 years old) and five experimental lighting systems with various configurations of auxiliary lighting. No experienced motorcycle riders or people with motorcycle riders in their immediate family were included as test subjects. Subjects viewed the approaching traffic on an active roadway (including a motorcycle) and indicated when it would and would not be safe to initiate their left turn across the approaching traffic. Jenness and his colleagues added a distracting element to the study by giving the subjects a secondary visual task that would, on occasion, occupy their attention. Jenness, et al. concluded that, on average, the safety margin that the test subjects gave the motorcycle did not differ significantly between any of the experimental lighting systems and the baseline lighting system. “However, having either low-mounted auxiliary lamps or modulated high beam lamps on the motorcycle significantly reduced the probability of obtaining a potentially unsafe short safety margin as compared to the baseline lighting treatment. Overall, the results suggest that enhancing the frontal conspicuity of motorcycles with lighting treatments beyond an illuminated low beam headlamp may be an effective countermeasure for daytime crashes involving right-of-way violations.”

Lenné and Mitsopoulos-Rubens [2011] reported a study in which they subjected 43 experienced drivers to a series of trials in a driving simulator. The task given to these subjects was to “turn ahead of an oncoming vehicle if they felt that they had sufficient room to do so safely.” In some trials, subjects had to turn in front of a motorcycle with its headlight on and, in other trials, the headlight was off. The gap available for the turn was also varied (short, medium, long). Lenné and Mitsopoulos-Rubens reported that “at short time gaps low-beam headlights may confer some benefit in gap acceptance by encouraging drivers to accept fewer gaps ahead of a motorcycle with headlights on than ahead of a motorcycle with headlights off. No statistically significant differences in gap acceptance between the headlight conditions were found at either the medium or long time gaps.”

Pai published a literature review related to motorcycle right-of-way accidents [2011]. He reported that “two major causes of such a crash scenario are the lack of motorcycle conspicuity and motorist’s speed/distance judgment error, respectively.” This appears to be imprecise language that means that some motorists did not see the motorcycles prior to the accident – and perhaps the motorcycle was not as conspicuous as it could have been – and other motorists did see the motorcycle prior to the crash but misjudged the timing of its approach. Pai continued: “A substantial number of studies have manipulated physical characteristics of motorcycles and motorcyclists to enhance conspicuity… Although various conspicuity aids have proven effective, some researchers reported that motorcyclist’s/motorcycle’s brightness per se may be less important as a determinant of conspicuity than brightness contrast between the motorcyclists and the surroundings…Research examining the effects of conspicuity measures on motorists’ speed/distance judgments when confronting motorcycles has been rather inconclusive.” In relationship to motorists’ judgments of approaching vehicles, Pai noted that “larger vehicles tended to be judged to arrive sooner than motorcycles. Such a speed/distance judgment error is likely attributable to some psychological effects such that larger automobiles appear more threatening than motorcycles. Older motorists particularly have difficulties in accurately estimating the distance and the speed of an approaching motorcycle.”

Crundall et al. [2012] noted that the most common cause of motorcycle collisions in the UK “was that of another vehicle pulling into the path of a motorcycle when exiting from a side road onto the main carriageway.” These authors observed that the statistics related to the number of look-but-fail-to-see collisions with motorcyclists may be inflated “by self-report biases. One could imagine alternative causes: a failure to look in the appropriate direction; or having looked and perceived the approaching motorcycle the car driver might fail to judge the level of risk that the conflicting motorcycle presents.” To further examine these issues, they developed a test in which subjects viewed video of an intersection on multiple screens simultaneously. The video was from the vantage point of a driver wanting to pull out at a T-junction and the screens were setup such that the subjects could turn their heads to the left and right to look for conflicting traffic. Crundall noted that “Mirror information was edited into the forward-facing video footage, providing a left-side mirror in the bottom-right of the left screen, a right-side mirror in the bottom-left of the right screen, and a rear view mirror at the top of the central screen. The three televisions were angled from each other at 120 degrees providing an immersive video, wherein participants could look to the left and right, as if looking through the side windows of their car, to check for conflicting vehicles on the main carriageway.” Both novice and experienced drivers were tested, as was a group of drivers with considerable experience driving both cars and motorcycles. “Specifically we were interested in when drivers first fixate the conflicting vehicles approaching the t-junction (when they look), how long they looked for (a measure of whether they perceive) and when they press a button to pull out from the junction (which, given that the necessary – but not sufficient – preconditions of looking and perceiving are met, can be considered a measure of appraisal).”

Crundall’s study included 74 test subjects – 25 novice car drivers with a mean age of 20.6 years and a mean experience level of 1.6 years; 25 experienced car drivers with a mean age of 33.4 years and a mean experience level of 14.8 years; and 24 drivers with significant experience with both cars and motorcycles (dual drivers) with a mean age of 44.9 years and a mean experience level of 25.7 years with cars and 20.0 years with a motorcycle. The videos used in the study include 10 scenarios with conflicting motorcycles, 10 with conflicting cars, and 10 with no conflicting vehicles. Conflicting vehicles could appear from either the right or the left. The clips included the approach phase to the T-junction, the stop, and then the time for the participants to make a decision about when they would pull out. Crundall also noted that “a further 42 clips (not analysed in the current paper) were randomly interspersed which required a different response; either a lane-change decision…or a hazard perception response. Participants could not predict when a hazard might appear, and thus had to remain vigilant to hazards even during the t-junction scenarios. Response times reflecting when the participants thought it was safe to pull out were recorded, along with the participants’ eye movements.”

Crundall reported that “the most immediate finding from the analyses was the greater caution given to conflicting motorcycles than to conflicting cars. Both the percentage of safe responses and the [reaction times] reflect a greater safety margin in responding to motorcycles… In regard to group differences, dual drivers were more cautious than the novice drivers, with the experienced group falling in between. This pattern held regardless of whether or not there was conflicting traffic. While the overall means improved with experience, the differentiation between motorcycle clips and car clips seemed greatest for the dual drivers followed by the novice drivers…dual drivers were the most sensitive to the presence of a conflicting motorcycle, while experienced drivers appeared the least sensitive.”

Crundall’s research suggests that car drivers who also ride motorcycles are more aware of approaching motorcycles and less likely to violate their right of way. This is consistent with the findings of other researchers. Maguzzu, et al., for instance, found that “having gained experience in riding any motorcycle…results in drivers being less prone to cause crashes with motorcycles with respect to drivers with no motorcycle license. It is reasonable to assume that car drivers who hold a motorcycle license have acquired more ability in riding and controlling two wheeled vehicles than drivers without a license. Therefore, it is possible to infer that some riding ability and knowledge of the risk annexed to riding, could protect drivers, maybe by helping them in the detection of oncoming motorcycles and the prediction of their manoeuvres” [2005].

Review of these studies leads to the following observations related to collisions where a passenger car driver violates a motorcyclist’s right-of-way and then states that they did not see the motorcyclists. First, for a driver to avoid an unsafe turn in front of a motorcyclist, they need to detect the motorcyclists. Then, they will need to make a judgment of acceptable accuracy about the time available to complete their turn before the motorcyclist arrives at the intersection. The following factors may contribute to drivers failing to detect approaching motorcyclists: a) inattention and distraction on the part of the driver; b) sight obstructions caused by the geometry of the intersection, by other traffic, or by the geometry of the driver’s vehicle; c) drivers not expecting to see motorcyclists on the road; or d) a lack of conspicuity of the motorcycle and rider. The following factors may contribute to drivers misjudging the time it will take for a motorcyclist to arrive at the intersection: a) excessive speed on the part of the motorcyclist and b) the small size and narrowness of the motorcycle and rider relative to other vehicles on the roadway. The influence of the motorcycle headlight and the rider’s clothing on the motorcycle being detected depends on the specific environment in which the accident unfolds and on how far away the motorcycle is when it needed to be detected.

References

Crundall, D., Crundall, E., Clarke, D., Shahar, A., “Why do car drivers fail to give way to motorcycles at t-junctions?” Accid. Anal. Prev. 44 (1), 88–96, 2012.

Gershon, P., Ben-Asher, N., Shinar, D., 2012. Attention and search conspicuity of motorcycles as a function of their visual context. Accid. Anal. Prev. 44 (1), 97–103, http://dx.doi.org/10.1016/j.aap.2010.12.015.

Hole, G.J., Tyrrell, L., Langham, M., “Some Factors Affecting Motorcyclists’ Conspicuity,” Ergonomics 39 (7), 946–965, 1996.

Hurt, H.H., DuPont, C.J., “Human Factors in Motorcycle Accidents,” SAE Technical Paper 770103, 1977, doi:10.4271/770103.

Jenness, J., Huey, R., McCloskey, S., Singer, J., Walrath, J., Lubar, E., Lerner, N., 2011. Perception of approaching motorcycles by distracted drivers may depend on auxiliary lighting treatments: a field experiment. In: Proceedings of the Sixth International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design, Lake Tahoe, CA, pp. 2–8.

Lenné, M.G., Mitsopoulos-Rubens, E., “Drivers’ decisions to turn across the path of a motorcycle with low beam headlights,” Proc. Hum. Factors Ergon. Soc. Annu. Meet. 55 (1), 1850–1854, 2011, http://dx.doi.org/10.1177/1071181311551385.

[NHTSA, 2017] National Highway Traffic Safety Administration, “Traffic Safety Facts – 2015 Data – Motorcycles,” DOT HS 812 353, https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812353, March 2017.

Olson, P.L., Halstead-Nussloch, R., Sivak, M., “The effect of improvements in motorcycle/motorcyclist conspicuity on driver behavior,” Hum. Factors 23 (2), 237–248, 1981.

Olson, P.L., “Motorcycle Conspicuity Revisited,” Hum. Factors 31 (2), 141–146, 1989.

Ouellet, J.V., 1990. Lane positioning for collision avoidance: an hypothesis. In: Proceedings: The Human Element: 1990 International Motorcycle Safety Conference, vol. 2, Orlando, Florida, pp. 9.58–9.80.

Pai, C.W., 2011. Motorcycle right-of-way accidents–A literature review. Accid. Anal. Prev. 43 (3), 971–982.

Sager, Bertrand, Yanko, Matthew R., Spalek, Thomas M., Froc, David J., Bernstein, Daniel M., Dastur, Farhad N., “Motorcyclist’s Lane Position as a Factor in Right-of-Way Violation Collisions: A Driving Simulator Study,” Accident Analysis and Prevention 72 (2014) 325-329.

ABOUT NATHAN

Nathan is an accident reconstruction expert at Kineticorp. He is dedicated to mastering his craft, and for the past 20 years, he has dedicated himself to research and writing as a means of developing authentic expertise that provides real value to juries. Nathan developed this article as part of the research that will ultimately make it into his book on motorcycle accident reconstruction. 

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