Title: Some Traffic Flow Relationships on Two-Lane Urban Streets : Final Paper
Abstract:The purpose of this study was to investigate some of the interrelation- ships of traffic flow variables on two-way two-lane urban arterial streets.The major variables considered were the relationships...The purpose of this study was to investigate some of the interrelation- ships of traffic flow variables on two-way two-lane urban arterial streets.The major variables considered were the relationships of speed, volume and density, and the distribution of observed headways.The study was performed on several types of urban arterial streets relative to the parking conditions.Six sites, selected in Lafayette and Indianapolis, were as identical as possible regarding roadway geometry and adjacent land use.The data were collected at each of the six sites by means of a continuously operating, traffic-actuated recording device.The traffic flow relationships investigated were analyzed by means of a multiple linear regression analysis for each individual site, each type of site and for each group of sites located within a particular city where the data were collected.The analysis indicated a slight decrease in mean speed with an increase in volume and average density and also an increase in average density with an increase in volume.These relationships appear to be linear for the range of data obtained for free-flowing traffic conditions.When other variables -commercial vehicles, directional distribution, and turning movements at nearby intersectionswere considered with the speed-volume relationship, volume was the only significant variable in explaining the variability in mean speed.In general, the proportion of explained variability was low.The relationships were not the same among site types located in different cities or among different site types located within the same city; however, the relationship was consistent among similar site types within the same city.A study of the observed headway distributions indicated that the volume of opposing traffic had very little influence upon the distribution of headways in a traffic stream, and then only when opposing volumes were very low.The observed distribution of headways for all volume levels indicated that more vehicles travel at shorter headways on rural highways than on the urban streets studied.The observed headway distributions were found to fit well in two theoretical distributions proposed in the litera- ture.Read More