The eastbound Wilshire Boulevard northbound on ramp to the 405 Freeway closed late Thursday for 90 days.
The on-ramp will be closed 24 hours a day. The closure is required to facilitate demolition of pre-existing ramp and to complete construction of the new fly-over ramp bridge.
The detour route is southbound Sepulveda Boulevard, right to westbound Santa Monica Boulevard, and right onto the Santa Monica northbound I-405 on-ramp.
An alternate route is southbound Sepulveda Boulevard, right onto westbound Pico Boulevard, right onto northbound Cotner Avenue, left onto the northbound I-405 Olympic Boulevard on-ramp.
Traffic control officers will be deployed to key intersections to assist with the adjustment of traffic patterns. Changeable message signs will be used to help direct drivers to designated detours.
While the original northbound on ramp from eastbound Wilshire had a length of 824 feet, the new on-ramp will have a length of 3,129 feet — a 280 percent increase in capacity.
The ramp is also being built to modern seismic standards.