PLEASANTON -- Construction begins Monday on a $1.4 million fix for a big traffic bottleneck -- the freeway entrance ramps from Bernal Avenue onto Interstate 680.

Bernal Avenue motorists trying to enter the freeway in the northbound and southbound directions face backups and aggravated collision risks. Under the current configuration, motorists on westbound Bernal Avenue face pinch points as they try to enter the freeway in either direction. Drivers must navigate from a single turning lane on Bernal into a single-lane on ramp.

The improvements will give motorists a second turning lane to enter the freeway and a second lane along part of the onramps. The northbound ramp will be widened as well.

"This will relieve the backup," said Ed Evangelista, a senior traffic engineer with the city. "It also will make things safer. Some drivers try to cut into the turning lane at the last minute before entering the freeway."

The congestion is especially bad when the Alameda County Fair is in session.

Development fees will pay for the project, Evangelista said. The worst congestion at this intersection comes from motorists entering the southbound freeway in the morning, and the northbound freeway in the afternoon, he said.

To make the area more pedestrian-friendly, contractors also will add a sidewalk along the south side of Bernal Avenue between West Lagoon Road and the freeway.

The project is expected to be complete in February. During the construction, the freeway ramps will be closed at times between 10 p.m. and 5 a.m. Announcements of those ramp closures will be posted in advance on the ramps.