Citation

Crisman B, Perco P, Robba A, Roberti R. Adv. Transp. Stud. 2007; 11: 19-32.

Copyright

(Copyright © 2007, Arcane Publishers)

DOI

unavailable

PMID

unavailable

Abstract

New and existing road safety evaluations use an important tool: the operating speed-profile. The operating speed-profile is particularly useful for alignment consistency evaluation in excessive speed differential identification and correct sight distance calculation needed along the road. Several operating speed prediction models for two-lane rural road tangents and curves have been developed. Using acceleration and deceleration rates representing actual rates drivers experience to join successive elements is needed in order for real speed-profile proximate operating speed-profile tracing. The authors investigated, on 18 two-lane rural road horizontal curves, driver speed reduction behavior and related geometric road characteristic dependence, in order for a deceleration model effective for operating speed-profile model use to be developed. Study results indicate the observed speed reduction behavior is not effectively described by a single constant deceleration rate, which means that the observed speed distance used for deceleration before a curve is wrongly estimated when it is used in a speed-profile model. There is significant variation between various curves in observed deceleration rates. An analysis of data reveals that speed reduction, approaching speed, curve length, and the radius are correlated to deceleration rate, and resulted in the development of two deceleration models. In regard to deceleration rate, the first estimates it as a function of impending curve radius, while the second estimates it as a function of speed reduction and approaching speed. Since they predict deceleration rates consistent with observed speed reduction behavior, and thereby closer real speed reduction distance deceleration lengths, these models can be used effectively for operating speed-profile construction.