M22-01. 20 Design Manual
Interchange Connections
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- Điều hướng trang này:
- Chapter 1360 Interchanges WSDOT Design Manual M 22-01.20 Page 1360-10 September 2021
- 1360.04(1) Lane Balance Design interchanges to the following principles of lane balance: 1360.04(1)(a) Entrances
- 1360.04(1)(b) Exits
| 1360.04
Interchange Connections To the extent practicable, provide uniform geometric design and uniform signing for exits and entrances in the design of a continuous freeway. Do not design an exit ramp as an extension of a main line tangent at the beginning of a main line horizontal curve. Provide spacing between interchange connections as given in Exhibit 1360-3. Avoid on-connections on the inside of a main line curve, particularly when the ramp approach angle is accentuated by the main line curve, the ramp approach results in a reverse curve to connect to the main line, or the elevation difference will cause the cross slope to be steep at the nose. Keep the use of mountable curb at interchange connections to a minimum. Provide justification when curb is used adjacent to traffic with a design speed of 40 mph or higher. Chapter 1360 Interchanges WSDOT Design Manual M 22-01.20 Page 1360-10 September 2021 Exhibit 1360-7 Lane Balance Merge C ³ A + B - 1 Diverge F = D + E - 1* B A C D E F *Note: Number of lanes (F) may increase by one lane, when the lane is an auxiliary lane between closely spaced entrance and exit ramps. 1360.04(1) Lane Balance Design interchanges to the following principles of lane balance: 1360.04(1)(a) Entrances At entrances, make the number of lanes beyond the merging of two traffic streams not less than the sum of all the lanes on the merging roadways less one (see Exhibit 1360-7). 1360.04(1)(b) Exits At exits, make the number of approach lanes equal the number of highway lanes beyond the exit plus the number of exit lanes less one (see Exhibit 1360-7). Exceptions to this are: • At a cloverleaf. • At closely spaced interchanges with a continuous auxiliary lane between the entrance and exit. In these cases, the auxiliary lane may be dropped at a single-lane, one-lane reduction off-connection (Exhibit 1360-21), with the number of approach lanes being equal to the sum of the highway lanes beyond the exit and the number of exit lanes. Closely spaced interchanges have a distance of less than 2,100 feet between the end of the acceleration lane and the beginning of the deceleration lane. Maintain the basic number of lanes, as described in Chapter 1210, through interchanges. When a two-lane exit or entrance is used, maintain lane balance with an auxiliary lane (see Exhibit 1360-8). The exception to this is when the basic number of lanes is changed at an interchange. |