Travel Time and Reliability Modeling on Urban Road Segments (The Case Study of Addis Ababa, Ethiopia)

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Nowadays, traffic congestion, delay and unreliability are terms that are most associated with present day travel. Transport users expend their precious time on long traffic queues and at the same time, fuel emission of vehicles increases in congested traffic conditions. Because of this and other problems, late arrival to work places and appointments for social or business activities have become common. And no study has developed a model for estimating travel time and reliability models on arterial roads. In this study a more general travel time and reliability model was developed. To study travel time probability distribution and reliability of a road segments in Addis Ababa city seven segments are selected. Seven segments were selected for the major modeling study. Manual method of data collection was used for collecting vehicle travel time and traffic volume data at peak hour for three days. Travel time data for two vehicle types were fitted to a probability distribution for each segment. Reliability of a road segment was analyzed using travel time reliability measures. Multiple linear regression models were developed to predict travel time reliability of a road segments. From the regression analysis all variables were found statistically significant to predict travel time reliability of a road segment. Traffic volume, segment grade, % of heavy vehicles, number of intersection legs, signal cycle length and segment length are negatively correlated with travel time reliability of a road segment while average segment width and average speed are correlated positively. An interaction effect in regression analysis was also developed to study the effects of interaction in regression model. A developed regression model can also be used to identifying these factors is a key contribution to HCM and AASHTO where studies are being conducted to include reliability factors into roadway design features. In addition to this correlation among the influencing factors, this is necessary for traffic operations, traffic design, and long-range transportation planning and it explains the contributing impacts of other factors on travel time reliability improvement on a corridor by modifying one factor.



Travel Time Reliability, Travel time reliability measurements, Regression model probability distribution