Adaptation Strategies for Managing Recurring Congestion—Adding New Capacity - Road Traffic Congestion - page 243

Fig. 17.8 Possible interchange connections that reduce congestion. Source Made by authors

combined with complex phasing. Corrective actions include changing the ramp
con gurations and building new connecting roadways.

Typical freeway-arterial street interchanges, with possible congestion — reducing

improvements are shown in Fig. 17.8 .

1. The cloverleaf intersection — once the solution to traf c congestion — has been

superseded by other ramp con gurations because of the space required and the

weaving on the freeway travel lanes. Sometimes two-phase traf c signals are

installed along the intersection of the arterial roadway and the exiting ramp
traf

c.
2. The partial cloverleaf is increasingly used since it eliminates weaving on the
freeway travel lanes. Ramp terminals at the interchange arterial street are con-
trolled by two-phase traf c signals. There are no left turns from the arterial

roadway to the freeway.
3. The diamond interchange is widely used because it requires less land and can be
integrated into the city street system where sometimes continuous one-way
frontage roads run parallel the main freeway. However, the arterial roads often
become congested at the interchange because of heavy overlapping left turns,
and because they need special traf c signal phases to accommodate them. Single

(and sometimes dual) left-turn lanes are provided along the arterial roadway.