M22-01. 20 Design Manual
(7) Loop Ramp Connections
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- Điều hướng trang này:
- 1360.04(8) Weaving Sections
- Chapter 1360 Interchanges WSDOT Design Manual M 22-01.20 Page 1360-21 September 2021
| 1360.04(7) Loop Ramp Connections
Loop ramp connections at cloverleaf interchanges are distinguished from other ramp connections by a low- speed ramp on-connection, followed closely by an off-connection for another low-speed ramp. The loop ramp connection design is shown in Exhibit 1360-27. The minimum distance between the ramp connections is dependent on a weaving analysis. When the connections are spaced far enough apart that weaving is not a consideration, design the on-connection in accordance with Section 1360.04(4) and the off-connection in accordance with Section 1360.04(5). 1360.04(8) Weaving Sections Weaving sections may occur within an interchange, between closely spaced interchanges, or on segments of overlapping routes. Exhibit 1360-14 gives the length of the weaving section for preliminary design. The total weaving traffic is the sum of the traffic entering from the ramp to the main line and the traffic leaving the main line to the exit ramp in equivalent passenger cars. For trucks, a passenger car equivalent of two may be estimated. Use the Highway Capacity Manual for the final design of weaving sections. Because weaving sections cause considerable turbulence, interchange designs that eliminate weaving or remove it from the main roadway are desirable. Use C-D roads for weaving between closely spaced ramps when adjacent to high-speed highways. C-D roads are not needed for weaving on low-speed roads. Chapter 1360 Interchanges WSDOT Design Manual M 22-01.20 Page 1360-21 September 2021 Exhibit 1360-14 Length of Weaving Sections Lane balanced weaving sections Lane imbalanced weaving sections 1000 2000 3000 4000 5000 6000 1000 3000 2000 T ot al W ea vi ng V ol um e, D H V Length of Weaving Section, L w (ft) Out of rea lm o f we avin g LO S B LO S C LO S D 2 ft 12 ft Required weaving length ( L w ) PC PT Edge of through lane or C-D road Note: To determine whether or not lane balance for weaving exists, see Exhibit 1360-9. |