Dr. Randy B. Machemehl presents bicycle study results to USIT students at UT Austin, July 2, 2012
Dr. Randy B. Machemehl, Nasser I. Al-Rashid Centennial Professor in Transportation Engineering at The University of Texas at Austin, presented “UT Bicycle Facility Research” on July 2, 2012, at the Cockrell School of Engineering as part of a series of presentations by and for students engaged in transportation research.
Dr. Machemehl discussed the results of work performed for three bicycle studies conducted through UT Austin’s Center for Transportation Research. The lecture was attended by Cockrell School of Engineering students, research faculty, and staff. The Undergraduate Summer Internship in Transportation (USIT) hosts the summer series.
Students participating in the USIT program are exposed to active transportation research programs that cover a wide range of topics, including systems analysis, materials, design, management, traffic engineering and planning, modeling, testing, and multimodal systems. USIT is sponsored by the Advanced Institute for Transportation Infrastructure Engineering and Management, an organization whose mission is to increase the number, quality, and diversity of professionals entering the transportation sector.
The first two bicycle safety studies Dr. Machemehl discussed were Operational and Safety Impacts When Retrofitting Bicycle Lanes (TxDOT Project 0-5157) and Operational and Safety Impacts for Bicyclists Using Roadways With On-Street Parking (TxDOT Project 0-5755). Both of these projects were funded by the Texas Department of Transportation. The third bike study examined four experimental bicycle safety devices. This study was funded by the City of Austin. All three studies were conducted through the Center for Transportation Research. UT Austin faculty and student researchers performed the research and produced research reports and products.
The purpose of Project 0-5157 was to provide guidance on the design of bicycle lanes added to existing roadways. Researchers conducted a literature review, analyzed crash data, and observed cyclists in Austin, Houston, and San Antonio. The study produced the Texas Bicycle Retrofit Workbook, an Excel application that evaluates the potential for bike lanes on roadways. The application evaluates roadway segments using a bicycle compatibility index (BCI) and passing event model (PEM). The BCI measures the cyclist comfort level based on surveys of cyclists about road and traffic conditions. The PEM estimates cyclist and motorist behavior during passing events based on measurements of cyclist and motorist lateral position during passing.
The workbook tools can be used to evaluate and compare alternate bicycle retrofit options, assess current roadways, and assist in planning during new construction.
Project 0-5755 followed up the first study by adding observation and testing of bicycle safety and operational impacts on streets that had on-street parking.
Observational studies for the two projects were conducted at 24 test sites in Austin, San Antonio, and Houston where 30 cyclists were paid to drive a set route and be observed by researchers in the field using video capture and analysis.
Analyzing the needs of the average bicyclists, researchers measured the space required for optimal travel: pavement space required from the bike wheel to the roadway gutter and total space needed on both sides of the bicyclist. Researchers also took into account the need for a “buffer” space needed between parked cars and bicyclist in order to avoid a bicyclist being injured by a collision with a parked car door being opened into the cyclist’s path.
The researchers concluded that motorist and cyclist behavior is significantly different in the presence of on-street parking. They also observed that, although total roadway width is critical to safety and operations for both cyclists and motorists, marked bike lanes are superior to unmarked wide outside lanes. They recommend that bike lanes be given a buffer zone in order to ensure that cyclists are removed from the door zone of parked vehicles. The additional information provided by Project 0-5755 has been added to the Texas Guide for Planned and Retrofit Bike Facilities and its associated Excel workbook.
The final study, which was performed in partnership with the City of Austin, examined four experimental bicycle safety devices: shared lane markings (sharrows), signage (“Bikes May Use Full Lanes”), colored bicycle lanes at conflict areas, and bicycle “boxes.” Researchers, in partnership with the City of Austin, observed selected locations where the four devices were installed. Using video surveillance, they measured bicyclist and motorist behavior before and after installation of safety devices.
Safe behavior for cyclists was defined as riding in the desired position in the roadway, obeying traffic laws and rules of the road. Safe motorist behavior was defined as drivers making a complete lane change when passing a cyclist, not encroaching on the cyclist’s space, while driving legally and observing the rules of the road.
Observation sites were multi-lane roadways downtown, near the UT campus, and arterial roads in the suburbs where commuter cyclists travel. Traffic volumes were between 200-275 vehicles per hour with bike speeds ranging 7-18 miles per hour with posted speed limits for motorists of 30-35 mph.
For the sharrows experiment, researchers concluded that sharrows held a strong potential to improve motorist and bicyclist safety when used as a standalone device or used as a tool to connect two facilities with and without bike lanes. When sharrows were present, cyclists tended to ride further from the curb and further away from the “door zone” of parked cars. Researchers observed improved motorist behavior as motorists more frequently changed lanes to pass, rather than encroaching on the bicyclist’s space. Motorists did not avoid the sharrow lane after installation.
Signage to remind motorists that bicyclist are allowed to use the full road lane was also studied, but the results where conflicting. In sparsely biked roadways, the safety facilities were deemed to have negative or inconclusive results, but in more heavily trafficked roadways, they showed positive results in driver and cyclist behavior. The presence of larger populations of commuter bicyclists significantly influences the effectiveness of signage.
The researchers expect that increased use of signage could increase safe driver and cyclist behavior, but more research is needed to determine whether this is the case.
Two other safety devices were tested and evaluated: colored lanes and “bike boxes” that provide designated areas for cyclists to wait at red lights that position them in front of cars. Bike boxes are intended to increase cyclist visibility to cars and prevent “right-hook” collisions at intersections. These types of safety facilities were installed in Austin at the intersection of Speedway and 38th Street and at the intersection of Shoal Creek Blvd. and Anderson Lane. Researchers observed the intersections and collected data.
There was a measurable increase in bike usage when the bike box was painted a solid color. Costs for both colored lanes and bike boxes can be $2,500-3,000 for each intersection approach. Under poor pavement conditions the painted areas can deteriorate quickly, yielding a short lifespan for marked pavement.
But the use of colored pavement markings to guide cyclists and cars through conflict areas showed an increase in motorist use of turn signals and in yielding to cyclists.
The final recommendations were as follows:
- Use sharrows when facility is too narrow to accommodate a bike lane.
- Use signs when sharrows are not financially feasible.
- Consider colored lanes when motorists are guided across a problem conflict area.
- Consider bike boxes when intersection has a high volume of bicyclists and moderate volume of motorists turning right on red.
The City of Austin study that tested these four bike safety facilities received an Innovative Projects Solutions Award from the Women’s Transportation Society. For more information on that award, visit this link.
Dr. Machememehl’s research expertise includes transportation and civil engineering, the application of microcomputers in transportation engineering, traffic engineering, transportation planning, and bicycle traffic safety studies. He is co-author on more than 70 published technical reports and research products published through the Center for Transportation Research.
Dr. Machemehl has been a faculty member at The University of Texas at Austin for 33 years. In addition to teaching UT students and conducting transportation research studies, he has served as the Director for the Center for Transportation Research (CTR) since 1999. Dr. Machemehl’s email is: email@example.com
Published reports related to the TxDOT funded research projects:
0-5157-1, Evaluation of On-Street Bicycle Facilities Added to Existing Roadways (PDF file)
0-5157-P2, Texas Guide for Retrofit and Planned Bicycle Facilities – Excel Workbook
(request information from CTR Library for this item at firstname.lastname@example.org )
0-5157-S, Adding Bicycle Facilities to Existing Roadways (PDF file)
0-5755-1, The Effects of On-Street Parking on Cyclist Route Choice and the Operational Behavior of Cyclists and Motorists (PDF file)
0-5755-S, Bicycle Facilities with On-Street Motor Vehicle Parking (PDF file)
Published reports related to the City of Austin funded study
Effects of Colored Lane Markings on Bicyclist and Motorist Behavior at Conflict Areas PDF file
Effects of Bicycle Boxes on Bicyclist and Motorist Behavior at Intersections PDF file
Effects of “Bicycles May Use Full Lane” Signs on Bicyclist and Motorist Behavior along Multi-Lane Facilities PDF file
Effects of Shared Lane Markings on Bicyclist and motorist Behavior along Multi-Lane Facilities PDF file
Links to More Information
Civil, Architectural & Environmental Engineering (CAEE) at UT Austin
Other links about the Sharrows project in Austin