[Table of Contents] [Chapter 1] [Chapter 2] [Chapter 3] [Chapter 4]

Background

A number of recent events renders a study of bicycle facilities as appropriate and timely. The passage of the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) legislation meant a variety of funds could be more readily used by local and state officials to plan and build such facilities. Indications are that many governments and agencies have taken advantage of the opportunity. Publication of the National Bicycling and Walking Study in 1994 with the U.S. Department of Transportation (USDOT) goals of doubling the percentage of trips made by bicycling and walking and simultaneously reducing by 10 percent the number of bicyclists and pedestrians injured or killed in traffic crashes adds emphasis to the need to accommodate non-motorists with well-designed facilities. User survey respondents have clearly stated that more facilities are desired and will increase the amount of travel by bicycle.

This research summary is intended to convey operational and safety information developed in a recent study of bicycle lanes (BLs) and wide curb lanes (WCLs). The document is based on the parent study titled A Comparative Analysis of Bicycle Lanes Versus Wide Curb Lanes (Hunter, Stewart, Stutts, Huang, and Pein, 1998).

A Brief Discussion of Bicycle Lanes and Wide Curb Lanes

A long-standing issue in the bicycling community centers on whether bicycle lanes or wide curb lanes are preferable. A bicycle lane (BL) is a portion of a roadway that has been designated by striping and pavement markings for the preferential or exclusive use of bicyclists (figure 1).

BL width is normally in the range of 1.2 to 1.8 m. A wide curb lane (WCL) is the lane nearest the curb that is wider than a standard lane and provides extra space so that the lane may be shared by motor vehicles and bicycles (figure 2). Thus, WCLs may be present on normal two-lane roadways or on multilane roadways. A desirable width for WCLs is 4.3 m. Lanes wider than 4.6 m sometimes result in the operation of two motor vehicles side by side. Many bicyclists report feeling safer when riding on BLs, while BL opponents venture that these facilities make it difficult for bicyclists to handle turning maneuvers at intersections, especially left turns. WCL advocates feel that these wider lanes encourage cyclists to operate more like motor vehicles and thus lead to more correct maneuvering at intersections.

Because a WCL is a wider-than-normal traffic lane that is shared with motor vehicles, some do not refer to this layout as a bicycle facility. However, for the purposes of this report, both BLs and WCLs will be referred to as bicycle facilities.

Parent Study Method

Overview

In the parent study, bicyclists in either a BL or WCL were videotaped as they approached and proceeded through eight BL and eight WCL intersections with varying speed and traffic conditions in three cities. Approximately 4,600 bicyclists were videotaped (2,700 riding in BLs and 1,900 in WCLs). The videotapes were coded to learn about operational characteristics (e.g., intersection approach position and subsequent maneuvers) and conflicts with motor vehicles, other bicycles, or pedestrians. A conflict was defined as an interaction between a bicycle and motor vehicle, pedestrian, or other bicycle such that at least one of the parties had to change speed or direction to avoid the other. Both bicyclist and motorist maneuvers in conflict situations were coded and analyzed. This would cover maneuvers such as a bicyclist moving incorrectly from the bicycle lane into the traffic lane prior to making a left turn, or conversely, a motor vehicle passing a bicyclist and then abruptly turning right across its path.

City Selection

Considerable effort in the early part of the project was spent in identifying possible cities for study. Candidates were narrowed and visits made to Santa Barbara, CA; the Palo Alto area of CA; Madison, WI; Gainesville, FL; and Austin, TX. Based on key factors such as amount and type of facilities, number of riders, willingness and eagerness of local contacts to participate, and windows of opportunity (i.e., climate) for videotaping, Santa Barbara, CA, Gainesville, FL, and Austin, TX, were selected as primary project cities (figure 3). These were spread geographically across the United States and provided for a good comparative analysis.

Site Characteristics

The objective was to achieve a group of sites within the cities that varied by width of BL or WCL (two levels), speed limit (two levels), and traffic volume (two levels). Such a matrix yields a total of eight sites. Thus, eight BL and eight WCL sites were selected for videotaping in each city. Selected breakpoint values were:

BL width - 1.5 m or less, >1.5 m

WCL width - 4.3 m or less, >4.3 m

Speed limit - 50 km/h or less, >50

km/h

Traffic volume - Low volume up to

7,500 vpd for 2 lanes; 15,000 vpd

for 4 lanes, +etc.

High volume greater than 7,500 vpd

for 2 lanes; 15,000 vpd for 4 lanes, etc.

We also tried to satisfy an objective of having 20 to 30 bicyclists per hour riding through the selected intersections. The BL and WCL matrices shown below provide the overall mix for all three cities combined.

As potential sites were selected in each city, we attempted to develop a mix based on the variable parameters shown above, as well as attempted to have variety in the sites that is representative of real-world conditions (e.g., BL and WCL sites with and without parking, BL sites with a weaving area and a bike pocket, BL sites with and without the stripe carried all the way to the intersection, BL and WCL sites where turning lanes were added at the intersection). In all three cities, however, the preliminary site list of top candidates had to be altered, usually due to a small number of riders available for videotaping. BL sites were generally popular and tended to have a reasonably high number of bicyclists available. Sometimes the preliminary list of BL sites was altered because it was discovered that the viewing angle for videotaping was not good. It was difficult to find eight suitable WCL sites in any of the selected cities due to small numbers of bicyclists riding on WCL facilities.

In Gainesville and Austin, the selected sites were quite close to the university campuses, because this is where the majority of the bicyclists were located, and data could be collected in an efficient manner. In Santa Barbara, the university campus was remote, and student bicyclists were a much smaller part of the mix. In the three cities selected, BL sites tended to concentrate at low traffic speed and low traffic volume locations, while WCL sites tended to concentrate at high traffic volume locations. Overall, the matrices of final sites indicate a reasonable mix of variation.

Besides the items mentioned above, a variety of other descriptive data items were collected at each site. These included type of area, pavement marking (striping) informa- tion for the BLs and WCLs, traffic control device present, number of lanes, estimated driving speed, presence of parking, average annual daily traffic (AADT), and others.

Videotaping of Bicyclists

The initial plan was to videotape bicyclists both at midblock and intersection locations. However, it became apparent that sample sizes would be relatively small if the videotaping task was divided in this fashion. Thus, the decision was made to forego the midblock videotaping and instead videotape each intersection twice for the following reasons:

• Intersections account for about half of all bicycle-motor vehicle crashes.
• Because of the need to make turning movements, intersections were expected to lead to more conflicts between vehicles, pedestrians, and other bicycles.
• It was of interest to learn about the maneuvers bicyclists make to travel through intersections, such as the ways left turns are made.
• The camera position would allow viewing of the approaching bicyclists from a considerable distance back from the intersection (not unlike a midblock situation).

Intersections and the approaches to intersections (referred to as midblock hereafter) were thus the focus of the data collection effort. Bicyclists were videotaped in the oncoming direction as they approached the selected intersections. The two-person data collection team usually mounted the camera on a 3-m stepladder set up some 30 to 40 m on the far side of the intersection. The location was such that the oncoming bicyclists generally were not

aware of the camera until close to the intersection. The stepladder was quite beneficial in providing a viewing angle above traffic. In a few of the Gainesville intersections, a platform truck belonging to the city was used to enable a better viewing position than could be afforded by a stepladder.

Normally the camera position allowed for a view of more than 150 m back from the intersection. Five 46-cm traffic cones were set up at 30-m intervals from the intersection stop bar location (at 30, 60, 90, 120, and 150 m). Approaching bicyclists were usually captured before reaching the 150 m cone and followed through the intersection (figure 4). The data collector would zoom in on the bicyclist to enable a better view of any kinds of bicycle-motor vehicle interactions. If the bicyclist had to stop for a traffic signal, the data collector would ascertain if it were possible to videotape another approaching bicyclist. If so, this bicyclist would be followed up to the intersection, and then both bicyclists would be taped as they rode through. Each intersection was videotaped twice for two hours at each session.

Generally all 16 sites in a city were videotaped once before the second round of taping began. As stated earlier, approximately 4,600 bicyclists were videotaped in the three cities (2,700 at BL sites and 1,900 at WCL sites).

Besides the bicyclist videotaping described above, 15-minute samples of traffic were also videotaped that corresponded to the time of the bicycle videotaping. The camera was positioned at a location where all the legs of the intersection could be observed. This videotape enabled counts of motor vehicles traveling through the intersection and thus some measure of exposure to traffic.

Bicyclist Experience Data

Bicyclist experience data were also collected separately from the videotaping at each of the 16 data collection sites in each city through use of a short oral survey.

Four questions were asked:

What is your age?

On average, how many days a week do you ride your bike?

On average, about how many miles do you ride each week?

How would you classify yourself with respect to the experience you have riding on city streets? (1 or 2, shown following)

1. I feel comfortable riding under most traffic conditions, including major streets with busy traffic and higher speeds.

2. I only feel comfortable riding on streets with less traffic and lower speeds, on streets with bicycle lanes, or on sidewalks.

In addition, information was coded pertain- ing to where the bicyclists were riding (road, sidewalk, or other location) as they approached the survey station, and the race, gender, and helmet use of the bicyclists. The data enabled information about the experience level of bicyclists riding through the particular intersection. Such knowledge could be directly relevant to the types of maneuvers and conflicts seen at the site. Each experience data collection session lasted 2 hours and was matched to the videotaping (i.e., same basic time of day and day of week) but was always done a few days before or after the videotaping.

Slightly more than 2,900 surveys were completed. These data were analyzed to learn about the age, riding habits, and experience levels of the bicyclists riding through these intersections.

Coding of Videotape Data

A form for coding a variety of items associated with a bicyclist approaching and riding through an intersection was developed, tested, and revised several times before the form was satisfactory. The objective was to code actions associated both with a "midblock" (the intersection approach) and an intersection area. Midblock was thus defined as the area between the third and fifth traffic cones set up on the approach leg ( 90-150 m from the intersection stop bar location). The intersection was defined as the area covered by the first three traffic cones (0-90 m back from the stop bar location).

The following are examples of the types of variables that were coded:

• Bicyclist riding wrong way.

• Bicyclist demographics and helmet use.

• Midblock positions and movements.

• Bicyclist spacing from the curb or gutter pan seam and from a passing motor vehicle.
• Bicyclist midblock behaviors (e.g., turning across a lane of traffic).

• Midblock conflict information.

• Intersection positions and movements.

• Bicyclist straight, left turn, and right turn methods.
• Bicyclist straight, left turn, and right turn conflict information.

Coding and Analysis of Crash Data

Two years of recent (1994 and 1995) bicycle-motor vehicle crash data were obtained from each of the three cities. Crashes from one complete year (1995) from each city were "typed" following the methodology originally developed by the National Highway Traffic Safety

Administration (NHTSA) in the late 1970s and being modified in partnership with the Federal Highway Administration (FHWA) for computer application. The computer software will be known as PBCAT (Pedestrian and Bicycle Crash Analysis Tool), a user-friendly software package developed for FHWA by the University of North Carolina Highway Safety Research Center. Crashes from each city were relatively sparse, and very few matched the intersections selected for videotaping. However, city trends could be examined to determine if overall crash patterns were similar to the types of behaviors and conflicts coded from the videotape data.

Organization of the Manual

Chapter 2 provides summary information from the parent study from all of the data sources listed above, including videotaping, bicyclist experience survey, and crash data. Problem situations found in BLs and WCLs are then highlighted. Chapter 3 recommends countermeasures for the problem situations, and Chapter 4 offers concluding comments.

[Table of Contents] [Chapter 1] [Chapter 2] [Chapter 3] [Chapter 4]