George Mason University
George Mason University Mason
George Mason University

Prediction Models for Free Flow Speed on Urban Streets

by Mohan Venigalla

Publication Details MORE LESS

  • Published Date: January 1, 2007
  • Volume/Issue: 1
  • Publisher: Transportation Research Board


This paper investigates the relationship between vehicle free flow speed and geometric variables on urban street segments. Geometric and spot speed data were collected from 35 different two lane segments located in Fairfax County in Virginia. To gain a better understanding of the relationships between free flow speed and geometric variables, speed data were visualized and descriptive statistics were computed. In addition to this, linear regression models were developed to estimate the relationship between mean free flow speed and roadside variables and 85th percentile free flow speed and roadside variables. The results showed a significant impact of posted speed limit on free flow speed. The predicted mean free speed at sites with 45 mph posted speed was found to be 5 mph and 8 mph higher than sites with 40 mph and 35 mph posted speed respectively. The other significant factors were found to be affecting free flow speed were the presence or absence of median and spacing between the signals.

Other Contributors

Asma Ali Aimee Flannery