BACKGROUND

The American Association of State Highway and Transportation Officials (AASHTO) defines design speed as “a selected speed used to determine the various geometric features of the roadway.  The assumed design speed should be a logical one with respect to the topography, anticipated operating speed, the adjacent land use, and the functional classification of the highway.”  The working definition for “target speed” is the operating speed that the designer intends for drivers to use. The topic of “design speed” versus “target speed” typically focuses on low-speed urban and suburban roadways, especially where the 85^th percentile speed is higher than the posted speed limit. Research is needed to gain a better understanding of how roadway, roadside, and non-roadway elements influence the operating speed—the actual speed of the driver—in order to improve roadway designs and reliably achieve desired speed outcomes.

OBJECTIVES

The objectives of this research are to (1) determine the effects of roadway, roadside, and non-roadway elements on operating speeds on roadways with a target speed between 30 and 40 mph and (2) develop recommendations on how the findings can be incorporated into the roadway design process.

RESEARCH PLAN

Task 1. Conduct data collection and analysis and prepare a Task 1 report. 

Task 2. Recommend a process by which appropriate roadway, roadside, and non-roadway elements should be considered to achieve a target speed. 

Task 3. Develop the final deliverables, which will include, at a minimum: (1) a final report documenting the entire research effort; (2) a practitioner’s guide that provides strategies on designing for target speed; (3) suggested modifications to standard references (e.g., HCM, and appropriate AASHTO Guides); (5) a PowerPoint-style presentation describing the background, objectives, research approach, findings, and conclusions; (6) a stand-alone technical memorandum titled “Implementation of Research Findings and Products”; and (7) a webinar for a diverse set of stakeholders.

STATUS

Research in progress.