Your odds of getting in a collision on the 120 Bypass as you near Highway 99 if you are trying to head south toward Ripon and Modesto is six times higher than the statewide average.

That tidbit from a Caltrans study helped set in motion the first phase of a $131.5 million project at the 120 Bypass and Highway 99  to improve vehicle movements and capacity. The project, expected to break ground a year from now, won’t be in place until 2023.

In the meantime Caltrans is taking steps aimed at reducing the potential for carnage until two lanes are in place for eastbound 120 Bypass heading toward Modesto are in place.

In the coming months Caltrans will place lane delineators and route shields on the pavement for eastbound 120 Bypass traffic as it approaches the Highway 99 interchange. Based on calls there was  an accident every 15 hours at the interchange and freeway approaches in 2018 that required Manteca Fire Department units to respond.

That is in addition to auxiliary lanes that will open in late November between the Main Street, Union Road, and Airport Way interchanges that are part of Manteca’s $28.4 million diverging diamond interchange at Union Road.

The Caltrans improvements are aimed at combatting the primary contributing factor to collisions — motorists in the left lane trying at the last moment to merge into the right lane that at peak periods when it is not at a virtual standstill is moving well below the posted speed limit due to congestion. What usually happens is the vehicle cutting in forces the cars in the right lane to hit their brakes. That has led to a high accident rate from vehicles already in the right land rear ending each other.

The shields, similar to what is on Interstate 5 southbound approaching the Interstate 205 interchange are designed to remind those that drive the route on a regular basis as well as alert those not familiar with the roadway what lanes keep going south on Interstate 5 and what lanes take you onto Interstate 205.

The 120 Bypass shields will designate north and south lanes for Highway 99.

The delineators are polyurethane “poles” that typically are 66 inches high. At some point past the Main Street onramp for the eastbound Bypass they will be placed along the stripping that separates the two lanes. Should cars veer into them they will cause minimal damage to vehicles. The idea is to eliminate last minute lane changes that can slow down traffic as well as create dangerous driving conditions.

It would force regular drivers heading toward Modesto that tend to be the biggest culprits in causing accidents to move over sooner.

Given it is normal for a severe slowdown or a backup to start 1.5 miles or so before the interchange, the addition of the auxiliary lanes will allow eastbound Bypass traffic to get out of the right-hand through lane sooner as well as allowing for an easier merge of those coming onto the eastbound Bypass from Union Road. That will further reduce the potential for rear-end collisions from the Slinky-effect that occurs during afternoon commute hours and other periods of heavy travel.

The new safety measures are the outgrowth of a 120 Bypass safety committee working with Caltrans and the California Highway Patrol that Manteca Councilman Gary Singh serves on.

In 2019 in a bid to improve safety Caltrans installed 2,700 feet of wider, 8-inch, double-white striped lane delineation, from just east of the Main Street overcrossing to the southbound Highway 99 connector ramp, is also to discourage last-minute lane changes. Crossing over double-white stripes is a traffic violation.

Stay In Lane signs were installed on both shoulders, just west of Van Ryn Avenue bridge, to help reduce the frequency of vehicles queue-jumping for southbound Highway 99 and sideswipe collisions. Watch For Stopped Vehicle signs were also installed on both shoulders, just west of the Main Street overcrossing, to help reduce the number of rear-end collisions.

Those improvements were made after Caltrans installed advisory signs on the Airport Way and Union Road  overcrossing advising motorists of the upcoming lane splits.

 The first phase of the interchange improveements involves:

*widening the eastbound 120 Bypass to southbound 120 Bypass from one to two lanes.

*removing the Austin Road overcrossing and replacing it with a longer span that ultimately would allow eight freeway lanes plus auxiliary lanes on Highway 99. The replacement bridge would span the Union Pacific Railroad tracks as well eliminating the at-grade crossing on Austin Road.

*adding a new connector road Austin Road to East Woodward Avenue. The existing railroad crossing on East Woodard Avenue would be modified to confirm with the new connector road and provide access to Moffat Boulevard.

*modifying the existing northbound Austin Road exit ramp to conform to the higher overcrossing profile of the replacement bridge.

*closing the northbound onramp and the southbound off-ramp for Highway 99 at Austin Road. The length of the closure is currently estimated at 9 years. Reopening of the replacement ramps will depend on the availability of funding for the third phase.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com