The pedestrian bridge overpass being built over the 120 Bypass at Union Road and its approaches may be the safest place in Manteca for pedestrians and bicyclists as well as being the most homeless-proof.
The design for the pedestrian’s bridge being built as part of California’s first diverging diamond interchange is designed with a tunnel under freeway ramps on both approaches so that pedestrians and bicyclists are separated from vehicle traffic.
Manteca Public Works Deputy Director Koosun Kim shared at a community meeting on the project conducted Tuesday at the Manteca Senior Center that the design team wanted to make sure that the project addressed all potential safety problems.
“In other communities the tunnels became places for the homeless to camp,” Kim said.
He also noted the design team was worried about the safety of pedestrians after dark from criminal elements.
As a result the tunnels will have:
uSecurity cameras placed and protected so they can’t be damaged to provide live feeds backs to the Manteca Police Dispatch Center.
uThere will be extensive lighting that will also be placed and protected in a manner where they can’t be damaged.
uThere will be a 24-hour emergency button tied in directly to the 9-1-1 system.
uIt will be equipped with a device that emits continuous noise that is extremely uncomfortable to hear for an extended period of time.
Kim said the city wants to avoid safety being compromised by homeless and others potentially camping in the tunnels. Noting that illegal encampments have been in place along freeways where decibel levels are high, Kim said the city is looking at several devices that emit high frequency noises.
While Kim did not elaborate on the devices being looked at, one such invention is dubbed “The Mosquito”. Wales-based Moving Sound Technologies invented it several years ago and is now selling the device in North America where a number of cities, park districts, and school districts activate them after hours when facilities are closed to deter vandalism.
The Mosquito, according to the firm’s website, has a small speaker that “produces a high frequency sound much like the buzzing of the insect it’s named after.”
Anyone loitering would soon hear a sharp, high pitched noise that has been described by some in urban areas such as Washington, D.C, where they have been placed to discourage people from gathering “as giving you a huge headache” if you linger for a minute or more.
The pedestrian bridge will be built on the east side of the existing overpass and will be 12 feet wide.
Pedestrians and others will drop down from street level at a grade that meets Americans with Disabilities Act standards, use a tunnel to go under the freeway ramps and then climb upward on a circular path to the bridge where they are protected from traffic with a barrier and then repeat the process in reverse on the other side.
Diverging diamond gets
high marks for safety,
efficiency, cost savings
Kim noted the diverging diamond design was chosen for a number of factors. It is a more effective use of funding, it improves safety and it improves traffic flow.
Caltrans District 10 has helped clear the way for the design that has been deployed in 80 plus other locations in the country with the nearest being on Mona Lane in Reno.
The flow across the freeway has lanes crossing to the opposite side of Union Road where the ramps are and then crossing back over at the ramps on the other side of the bridge.
Where the traffic crisscrosses there are traffic signals. On a traditional overpass turn movements on and off the freeway would also go through the traffic signals. That’s not the case with a diverging diamond interchange.
If Union Road was improved to a partial cloverleaf interchange as was originally envisioned there would be 24 conflict points for vehicles. The diverging diamond has 12.
Even more significant is the reduction in the potential for frequent T-bone crashes that can result in extensive property damage and serious injury. There are 20 such conflicts on a traditional interchange and just two on a diverging diamond. Those two would be where the north and south lanes on Union Road crisscross.
Due to the interchange’s geometry the average speed is slowed from 40 mph to 25 mph.
Auxiliary lanes will be
constructed in 120 Bypass
between Airport & Main
The project will also allow a left turn pocket to be placed so southbound Union Road traffic could turn onto Lifestyle Street that passes on the south side of JC Penney at The Promenade Shops at Orchard Valley. It means traffic trying to access the western part of Orchard Valley from southbound Union would not need to travel to the Atherton Drive signal and make a left turn to access an entrance off Atherton or make a U-turn to go back to Lifestyle Street.
The project will also include constructing auxiliary lanes from Union Road along the 120 Bypass to Airport Way and Main Street in both directions to allow a much smoother weave in and out of freeway traffic. Ramp metering signals will also be installed.
The partial cloverleaf design would have required the existing bridge be demolished. The diverging diamond doesn’t require the bridge’s removal. Instead a second bridge will be built on the west side and joined to the existing structure.
The design chosen by the city eliminated the need for right-of-way acquisition as well as the expensive bridge tear down. That means three things: A shorter construction time frame, minimal traffic disruption during construction, and a savings of $10 million.
The diverging diamond with the pedestrian bridge component comes to $26 million as opposed to $36 million for a partial cloverleaf without a pedestrian bridge.
Kim noted that when the need comes down the road to widen Union Road’s sister interchanges on the 120 Bypass — Airport Way and Main Street — a similar diverging diamond design could be employed.
The project is expected to break ground this summer with work completed in the fall of 2019.
To contact Dennis Wyatt, email firstname.lastname@example.org