Work to Start on Widening Traffic-Snarling El Toro Y : Freeways: The project will create the world’s widest interchange--up to 26 lanes--and will cost $105 million.

IRVINE —  Work crews began preparations Monday for transforming the El Toro Y into the world’s widest freeway interchange--26 lanes at one point.

Signs explaining the $105-million reconstruction project and its funding started going up at the site, the junction of the Santa Ana and San Diego freeways in Irvine.

Later this week, concrete barriers will be moved into place, and mounds of dirt will be piled for new bridge and ramp structures at what is one of Orange County’s worst traffic bottlenecks.

Included in the project, due to be completed in 1996, are new on- and off-ramps at Bake Parkway and special ramps to connect car-pool lanes on one freeway with the car-pool lanes on the other.

Officials don’t want motorists to look, however, because gawkers slow traffic, causing long delays. To help reduce the temptation, highway workers will install plywood barriers known as gawk screens atop the concrete separators.

Michelle Peterson, project spokeswoman, said officials want to wait a few days after the signs are put up before doing actual construction so that motorists have a chance to acquaint themselves with the work.

More than 300,000 vehicles a day pass through through the El Toro Y, with another 100,000 expected by the year 2010.

The reconstruction effort is being funded mostly by Measure M, the half-cent sales tax for traffic improvements approved by Orange County voters in 1990.