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Crosswalk Marking Field Visibility Study

CHAPTER 2. LITERATURE REVIEW

LABORATORY EVALUATION

SPEED EVALUATIONS

LABORATORY EVALUATION

Knoblauch et al. conducted a laboratory evaluation of alternative crosswalk markings in the late 1980s.⁽²⁾ Researchers projected 35–mm slides of pictures that represented crosswalk markings located at 300, 400, or 500 ft. Preliminary tests included markings at shorter and longer distances, but they were eliminated because they were either always correctly identified (shorter distances) or were almost indiscernible (longer distances). The 59 subjects were told that the slides might show a crosswalk, lettering, or even nothing. The subjects were asked to indicate on an answer sheet, to the best of their ability, what they could see: nothing, something (unsure if it was a crosswalk or lettering), lettering, or a crosswalk. A score of 3 was assigned to the pattern if the subject correctly identified the marking at all three distances (300, 400, and 500 ft), a 2 was assigned if the markings were correctly identified at two of the three distances, and so on. The crosswalk marking patterns tested are shown in table 1.

The authors concluded that one class of pattern emerged consistently as the best–the ladder crossings. Within the ladder group, there was minimal difference between three different patterns that had spacing of 12 or 24 inches between the stripes. The pattern that used the greatest spacing, 48 inches, did not test as well (2.2) as the other ladder patterns (2.8, 2.7, and 2.8).

Using the provided scores, an estimate of where the ladder markings were detectable was calculated to be about 400–500 ft. The authors did not provide the scores for the other markings, so a comparison with the viewing distance to a transverse marking or to word markings cannot be made.

Table 1. Patterns tested by Knoblauch et al.⁽²⁾

Test	Description	Sketch (not to scale; but approximate proportions)
1	6–inch wide edgelines
2	12–inch wide edgelines
3	24–inch wide edgelines
4	12–inch diagonal stripe with 12–inch space
5	12–inch diagonal stripe with 24–inch space
6	12–inch diagonal stripe with 48–inch space
7	12–inch diagonal stripe with 48–inch space with 8–inch edgelines
8	24–inch diagonal stripe with 24–inch space
9	24–inch diagonal stripe with 48–inch space
10	12–inch ladder stripe with 12–inch space
11	12–inch ladder stripe with 24–inch space
12	12–inch ladder stripe with 48–inch space
13	24–inch ladder stripe with 24–inch space
14	24–by–12– inch box with 24–inch spaced edgelines
15	24–by–12–inch box with 36–inch spaced edgelines
16	24–by–12–inch box with 48–inch spaced edgelines
17	Transverse word marking STOP	STOP
18	Transverse word marking ONLY	ONLY

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SPEED EVALUATIONS

Speed has also been used as a measure of effectiveness for crosswalk markings. In August 2000, Knoblauch and Raymond reported on the effects of crosswalk markings on vehicle speeds at six sites located in three States.⁽³⁾ All sites were at uncontrolled intersections that had been recently resurfaced and had a speed limit of 35 mi/h. Before speed data were collected after the centerline and edgeline delineation was installed but before the crosswalk was installed. After data were collected after the crosswalk markings were installed for three conditions: no pedestrian present, staged pedestrian looking, and staged pedestrian not looking. The results indicated a slight reduction in speed at most, but not all, of the sites (typically on the order of 1–3 mi/h). Overall, there was a significant reduction in speed under both the no pedestrian and the pedestrian not looking conditions. The authors noted that "any speed reduction in response to the crosswalk marking alone (e.g., with no pedestrians present) is somewhat surprising. The crosswalk markings are intended merely to inform drivers to slow and prepare to yield to a pedestrian if one (or more) is present. It is technically not necessary to slow down unless a pedestrian(s) is present." The authors concluded, "it appears that drivers are aware of–and respond to–crosswalk markings by slowing down slightly. It also appears that drivers react differently to the different pedestrian scenarios that were staged. They are more careful (e.g., they slowed more) when the pedestrian does not appear to be paying attention to approaching traffic, and this is the situation where they, as drivers, need to be especially careful."

In August 2001, Knoblauch et al. reported on research that determined the effect of crosswalk markings on driver and pedestrian behavior at unsignalized intersections.⁽⁴⁾ A before/after evaluation of crosswalk markings was conducted at 11 locations in 4 U.S. cities. It was found that drivers approach a pedestrian in a crosswalk somewhat slower. No change was found in driver yielding. The vehicle speed and staged pedestrian study involved a comparison of vehicle speeds before and after crosswalk markings were installed. Vehicle speeds were measured at two locations (approach speed and crosswalk speed) under three separate pedestrian conditions (no pedestrian present, staged pedestrian standing in crosswalk looking in the direction of oncoming traffic, and staged pedestrian in crosswalk making a stepping motion as if he/she were about to step into the roadway). For the "Ped Looks" condition, speed reductions were found at all locations. The magnitude of the speed reductions varied from 0.2 to 2 mi/h. For the "Ped Steps" condition, the approach speeds in Sacramento and Buffalo decreased significantly (between 0.4 and 2.1 mi/h) and the approach speeds in Richmond increased significantly, which was not expected. The authors found that there was no difference in approach speed when no pedestrian was present. They noted the following:

"This was expected since there is no need for a driver to slow down when approaching a crosswalk unless a pedestrian is present. The purpose of the crosswalk marking is to produce a change in driver awareness. The markingsshould be telling the driver that pedestrians may be present and, if they are present, they may cross the road at that location. Basically, the desired driver response to a marked crosswalk is: 'There may be a pedestrian here; I need to be careful' or 'If I see a pedestrian here, they may cross; I need to be careful.' It is not essential that the driver slow down. Unfortunately, there is no way to observe or measure driver awareness, so vehicle speed is used as a kind of surrogate measure."

While decreases in speed on the approach to a crosswalk may indicate that drivers are more alert to their surroundings, the preference is to use more direct measures. Knoblauch et al. stated that there is no way to observe or measure driver awareness.⁽⁴⁾ However, there may be methods available in certain situations, such as laboratory or instrumented vehicle settings. For example, an eye tracker or dashboard camera can be used to measure if drivers increase their search of the roadside for potential pedestrians when they detect and recognize crosswalk markings. These settings could also provide information on the distances that drivers can detect and recognize crosswalk markings with or without signs.

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FHWA-HRT-10-068