Effect of on-ramp demand and flow distribution on capacity at merge bottleneck locations

ABSTRACT

Past research acknowledged the impact of ramp vehicles on the occurrence of a breakdown event, but little has been done to quantify the effect of the ramp vehicles on the resulting bottleneck capacity. The objective of this research is to explore the relationship between ramp flow and capacity and to recommend capacity values for merge bottleneck locations. To explore the relationship between ramp flow and capacity, a capacity model has been developed using linear regression. The Kansas City area freeway network was considered for the analysis. Multiple locations that experienced ‘true breakdowns’, i.e., breakdowns caused by merging operations and not due to downstream spillback, were selected for the analysis. Demand-derived variables such as ramp-to-freeway demand ratio and flow distribution were found to be statistically significant. The regression model was used to predict capacity values for different ramp and freeway demands. By observing the calculated capacity values it was concluded that capacity decreases as the ramp-to-freeway demand ratio increases.

KEYWORDS:

• Ramp-flow ratio
• merge bottleneck
• pre-breakdown capacity
• flow distribution

Acknowledgments

The authors would like to thank KC Scout for providing the traffic data for this research.

Disclosure statement

No potential conflict of interest was reported by the authors.