Abstract
Merging on motorways represents one of the most difficult and dynamic maneuvers of all driving subtasks. Merging operations at uncontrolled ramp junctions have been extensively investigated. With the rapid implementation of ramp metering techniques, many junctions are now operated under ramp metering control. Little research has been done to investigate the possible effects of ramp metering on the merging operation. The research described in this paper focuses on the comparisons of merging operations under both metered and unmetered scenarios. Time series data of the merging process were collected with the Transportation Research Group instrumented vehicle and video cameras at a tapered motorway merge site. The data included accurate vehicle speed measured by laser speedometer, leading and following headway measured by radar, and driver's eye movement derived from an in-car camera. Following a comprehensive analysis of the data, it was found that merging operations under ramp control could be significantly different from free merging. Merging maneuvers may become more difficult as a result of ramp control. The equity implications of such effects are discussed. It is believed that the understanding gained from this research will be useful for the design and operation of ramp metering.