Motorists on  westbound I-580 in Livermore will encounter an unusual traffic obstacle late tonight -  a three hour freeway closure. The closure of all westbound freeway lanes at North Livermore Avenue will last from 12:01 to 3 a.m. Thursday, and repeat the same hours early Friday.

Caltrans said it needs the closures to accommodate construction of the I-580/Highway 84 interchange at Isabel Avenue.

Caltrans also urges  motorists to prepare for lane closures leading up to the full westbound closures. Signs will direct motorists to a detour to exit the freeway and then reenter further to the west.