✍ Scribed by Bin Ran; Shawn Leight; Ben Chang
No coin nor oath required. For personal study only.
The automated highway systems (AHS) are not designed as stand-alone transportation facilities. Drivers will by necessity drive from their origins to the AHS entrance, and from the AHS exit to their ®nal destinations. Therefore, the AHS will aect other transportation facilities, and should be integrated with all other facilities in the transportation system. Interfaces create much of the congestion for todayÕs transportation systems. Likewise, AHS interfaces may cause a similar problem, due to either AHS interactions with conventional systems or internal limitations from AHS merging capabilities. If these problems exist, either the AHS or the conventional road network cannot function properly. Consequently, the system as a whole may break down and the AHS could potentially become a detriment to the overall transportation system.
Clearly, not enough is known about the automated merging process to determine what conditions would lead to congestion at interface points. The current macroscopic analysis techniques assume parameters that are not applicable to an AHS, and no detailed AHS merging models have been developed and validated. This paper addresses the interface problem between an AHS, and conventional roadway. Speci®cally, it presents a microscopic simulation model for one scenario of the automated merging maneuver. The results of the model show that for low ¯ows and conventional highway speeds, an one-lane AHS merging section with a dedicated automated entrance ramp has many similar characteristics as a two-lane conventional freeway with or without ®xed-time ramp metering. However, when the conventional freeway starts to ``break down'' near its capacity, the AHS continues to perform with little delay. The model also validates that the minimum ramp length requirements are a function of the merging vehicleÕs speed, the mainline vehiclesÕ speed, and the acceleration and deceleration rates of the merging vehicle.
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