John A Molino

Pedestrian and Bicyclist Exposure to Risk: Methodology for Estimation in an Urban Environment

There is currently no commonly accepted or adopted measure of pedestrian and bicycle exposure to risk. Consequently, a large portion of the field of pedestrian and bicycle safety is lacking an adequate means to evaluate the effectiveness of its efforts. The current study presents a proposed metric for measuring pedestrian and bicycle exposure to risk: hundred million pedestrian or bicycle miles of roadway (or other motor vehicle shared facility) traveled. A method for implementing the proposed exposure metric is described for eight shared-facility types characteristic of the urban environment of Washington, D.C. These facilities include three types of intersections, midblock road segments, driveways, alleys, parking lots, parking garages, school areas, and areas with playing, dashing, and working in the roadway. The methodology is then used to calculate the annual pedestrian and bicycle exposure for the city for the calendar year 2007. The results of these calculations revealed 0.82 hundred million miles for pedestrian exposure and 0.37 hundred million miles for bicyclist exposure. In this way both the feasibility and scalability of the proposed metric were successfully demonstrated for a relatively large urban environment. Thus the proposed metric has the potential to eliminate one of the major obstacles in the pedestrian and bicycle safety field, the lack of adequate exposure data. Although further refinement and validation are still needed, the proposed metric provides a possible initial foundation to develop a national unit of risk exposure for pedestrians and bicyclists.

Segway Rider Behavior: Speed and Clearance Distance in Passing Sidewalk Objects

The Segway Human Transporter is becoming more prevalent on urban sidewalks. This experiment investigated the approach speed and passing clearance that Segway devices exhibit on encountering a variety of obstacles on the sidewalk. The experiment was conducted with a sample of 20 Segway operators: 10 experienced operators and 10 novices. For the given experimental course and procedures, the results of the study revealed that (a) Segway riders approach obstacles at a mean speed of about 4.5 mph (7.2 km/h) with a range from 2.7 mph (4.3 km/h) to 6.8 mph (10.9 km/h); (b) Segway riders pass obstacles with a mean clearance of about 14.5 in. (36.7 cm) with a range from 3.3 in. (8.4 cm) to 43.2 in. (110 cm); (c) Segway riders pass moving pedestrians at an average speed of about 5 mph (8.1 km/h) and with an average clearance of 35.9 in. (91.2 cm); (d) Segway riders pass obstacles more slowly by about 0.5 mph (0.8 km/h) on average and closer by about 17.6 in. (44.7 cm) on average on a narrow as opposed to a wide sidewalk; and (e) experienced Segway riders pass faster by about 1.9 mph (3.1 km/h) on average than do novice riders. In the current experiment, the average passing event involving a Segway rider and a pedestrian required a minimum total distance of approximately 7.0 ft (2.1 m). These data should assist engineers in calculating the impact of various mixes of Segway traffic on sidewalks.

Relative luminance of retroreflective raised pavement markers and pavement marking stripes on simulated rural two-lane roads

The FHWA Turner-Fairbank Highway Research Center is undertaking a research program to study the visibility of retroreflective raised pavement markers (RRPMs). The focus of the initial effort is to determine the relative luminance of RRPMs and pavement markings (PMs) needed to produce adequate guidance on rural two-lane roadways at night. A driving simulator was used to test 36 research participants as they drove simulated roadways containing various combinations of RRPMs and PMs. The luminance of the simulated roadway delineation ranged from 0.07 to 4.1 cd/m2. The primary driver performance measure was curve-recognition distance. For the various RRPM and PM luminance conditions, mean curve-recognition distances ranged from 19.0 m (62.3 ft) to 68.4 m (224 ft), with a grand mean of 43.0 m (141 ft). Regression analyses produced predictive equations to estimate the mean curve-recognition distance from the luminance of RRPMs acting alone or of PMs acting alone. Trading ratios were computed for PM luminance with and without RRPMs present on the road. A conservative empirical estimate of 0.52 was computed for such a trading ratio based on the data from the current experiment. This value compared favorably with independent estimates of 0.54 and 0.55 based on an earlier analytical approach. Thus, the current experiment confirmed, with empirical data, earlier estimates that it might be possible to reduce the luminance of PMs on rural two-lane roads by about 45% when appropriate RRPMs are installed.