M22-01. 20 Design Manual
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- 1360.04(4)(a) Acceleration Lane
| Chapter 1360
Interchanges WSDOT Design Manual M 22-01.20 Page 1360-13 September 2021 1360.04(4) On-Connections On-connections are the paved areas at the end of on-ramps that connect them to the main lane of a freeway. They have two parts: an acceleration lane and a taper. The acceleration lane allows entering traffic to accelerate to the freeway speed and evaluate gaps in the freeway traffic. The taper is for the entering vehicle to maneuver into the through lane. On-connections are either tapered or parallel. The tapered on-connection provides direct entry at a flat angle, reducing the steering control needed. The parallel on-connection adds a lane adjacent to the through lane for acceleration with a taper at the end. Vehicles merge with the through traffic with a reverse curve maneuver similar to a lane change. While less steering control is needed for the taper, the parallel is narrower at the end of the ramp and has a shorter taper at the end of the acceleration lane. 1360.04(4)(a) Acceleration Lane Provide the minimum acceleration lane length, given in Exhibit 1360-10, for each ramp design speed on all on- ramps. When the average grade of the acceleration lane is 3% or greater, multiply the distance from the Minimum Acceleration Lane Length table by the factor from the Adjustment Factor for Grades table. For existing ramps that do not have significant crashes in the area of the connection with the freeway, the freeway posted speed may be used to calculate the acceleration lane length for Preservation projects. If corrective action is indicated, use the freeway design speed to determine the length of the acceleration lane. The acceleration lane is measured from the last point designed at each ramp design speed (usually the PT of the last curve for each design speed) to the last point of the ramp width. Curves designed at higher design speeds may be included as part of the acceleration lane length. tải về 1.86 Mb. Chia sẻ với bạn bè của bạn:
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