A safe passage for bicyclists to cross the 120 Bypass may not be included in directions given to a firm the Manteca City Council may hire to design the new Union Road interchange.
A staff memo recommends the council not include a grade separate bicycle/pedestrian path unless funds are obtained from a non-city source. While the bridge would still have sidewalks, it would not have a separated bicycle path as previous councils have adopted as a city policy as part of the Manteca traffic circulation plan as well as the bike trail system master plan that the Tidewater Bikeway serves as a backbone.
The City Council on Tuesday is being asked to hire Mark Thomas & Company for $1.6 million to provide engineering, right-of-way acquisition, and environmental work for the interchange. The council meets at 7 p.m. at the Civic Center, 1001 W. Center St.
The new overpass is being funded with money collected from growth as well as unspent redevelopment agency funds that were earmarked for the Union Road project.
Over past years residents that live south of the 120 Bypass have expressed concern about improving bicycle and pedestrian safety for children and others that cross the 120 Bypass on foot. The only separated bicycle/pedestrian path goes under the 120 Bypass at Van Ryn Avenue. The need for safe passage for people not in vehicles also has been brought up in discussions about the need for a satellite library south of the 120 Bypass.
Manteca is looking at using a diverging diamond interchange for Union Road instead of upgrading the existing structure to a partial cloverleaf.
Traffic lanes cross on either side of the bridge structure of a diverging diamond interchange so northbound traffic would cross the bridge on the west side instead of the east side with the southbound lanes on the east side instead of the west side. Once they clear the bridge they are switched back.
The on and off ramps along with the flipping of the lanes creates two semi-diamond shaped intersections on either side of the bridge. This eliminates the need for traffic from both directions on Union Road as well as that coming from the 120 Bypass to use traffic signals to exit an off ramp or to get into an on ramp. The project will also include ramp meter signals such as now are in place on the Lathrop Road/Highway interchange.
The design could slash as much as $10 million from the $25 million estimated cost of converting Union Road into a partial cloverleaf.
Other advantages of a diverging diamond interchange according to Advanced Transportation Solutions/American are:
Fewer conflict points (14 for diverging diamond design, 26 for conventional design).
Better sight distance at turns.
Traffic calming features when desired.
Additional right of way is rarely needed.
Virtually no driver confusion based on a study and observation of existing diverging diamond design interchanges.
Construction time is reduced.
Wrong way entry to ramps extremely difficult.
Pedestrian crossings are shorter.
Maintenance of traffic is simplified during construction.
There are 57 such interchanges now in place in the United States. The closest is in Reno on Interstate 580 at Moana Lane.