Paper Details

TRB 91st Annual Meeting (January 22-26, 2012)

Event Number:	432
Event Title:	Research for the Sake of Safety
Event Date:	Jan 23 2012 7:30PM- 9:30PM
Event Location:	Marriott, Virginia A
Event Description:
Event Agenda:

How Far Are Current Advisory Speeds from Being Optimal? Analysis Based on Safety Performance (12-4728)

Posting advisory speed signs at sharp horizontal curves to provide the driving public with a safe speed is a practice well established in the United States. The operational effectiveness of these signs has long been questioned in the current literature. The authors of this paper recently developed a function to model the expected safety effect of these signs. The function stems from a statistical analysis on crash data from 2-lane rural highways in the state of Oregon. In general, that research effort found that advisory speed signs tend to enhance safety. However, the authors also determined that advisory speed signs may not be displaying the value with the greatest potential for safety enhancement. Since the derived function proved meaningful from the engineering and human factors perspectives, these authors then extend the use this function to compute and recommend the theoretically ï¿½optimalï¿½ advisory speed. A new posting procedure resulted from this effort. The authors compared the expected performance of advisory speeds from the proposed procedure to the speeds derived from current posting guidelines. A comparable performance suggests that current guidelines are close to the hypothetically ï¿½optimalï¿½ advisory speed. In general, both the current and new computational methods performed better than speeds determined by the ball bank indicator method. This paper also presents a field validation analysis of the engine function of the new posting method. The results confirmed the meaningfulness of the function, and therefore, of the potential benefit for determining safety-based advisory speeds with the method proposed in this paper.

Authors
     Avelar, Raul E., Texas A&M Transportation Institute
     Dixon, Karen K., Texas A&M Transportation Institute