M22-01. 20 Design Manual
tải về 1.86 Mb. Chế độ xem pdf
|
- Điều hướng trang này:
- 1360.03(7) Ramp Meters
| Chapter 1360
Interchanges WSDOT Design Manual M 22-01.20 Page 1360-9 September 2021 1360.03(6) Ramp Lane Increases When off-ramp traffic and left-turn movement volumes at the ramp terminal at-grade intersection cause excessive queue length, it may be desirable to add lanes to the ramp to reduce the queue length caused by congestion and turning conflicts. Make provision for the addition of ramp lanes whenever ramp exit or entrance volumes are expected to result in an undesirable mobility or safety performance. (See Chapter 1210 for width transition design.) 1360.03(7) Ramp Meters Ramp meters are used to allow a measured or regulated amount of traffic to enter the freeway. When operating in the “measured” mode, they release traffic at a measured rate to keep downstream demand below capacity and improve system travel times. In the “regulated” mode, they break up platoons of vehicles that occur naturally or result from nearby traffic signals. Even when operating at near capacity, a freeway main line can accommodate merging vehicles one or two at a time, while groups of vehicles will cause main line flow to break down. The location of the ramp meter is a balance between the storage and acceleration criteria. Locate the ramp meter to maximize the available storage and so that the acceleration lane length, from a stop to the freeway main line design speed, is available from the stop bar to the merging point. With justification, the average main line running speed during the hours of meter operation may be used for the highway design speed to determine the minimum acceleration lane length from the ramp meter. (See Section 1360.04(4) for information on the design of on-connection acceleration lanes and Chapter 1050 for additional information on the design of ramp meters.) Driver compliance with the signal is required for the ramp meter to have the desired results. Consider enforcement areas with metered ramps. Consider HOV bypass lanes with ramp meters. (See Chapter 1410 for design data for ramp meter bypass lanes.) tải về 1.86 Mb. Chia sẻ với bạn bè của bạn:
|