By Tim Hunt
CalTrans explains its rationale for unnecessary ramp meteringUploaded: Nov 3, 2020
One thing you can count on in October during election years is groundbreaking or ribbon cutting ceremonies.
So, it was last week that transportation officials and CalTrans virtually cut the ribbon on northbound express lanes from Auto Mall Parkway in Fremont to Highway 84 in Sunol. By next spring, the lanes will run from Milpitas all the way to Martinez giving solo drivers the option of paying tolls and being free to vehicles carrying two or more people. Southbound lanes and northbound lanes are still under construction. That will include the final Alameda County stretch from Highway 84 to Stoneridge Drive.
The project included 16 ramp meters with both HOV and general traffic lanes. The project cost an estimated $26.5 million including the ramp work, closed circuit televisions, message signs as well as the lane expansions. Ramp metering was implemented on southbound ramps in 2011 according to a CalTrans spokeswoman who responded by email. The project included huge retaining walls in Fremont and on the Sunol Grade to accommodate the additional lanes on the new nine-mile stretch.
It’s welcome news to afternoon commuters who battled hours of congestion in the pre-pandemic days.
What’s striking to me is why CalTrans engineers thought it was necessary to install metering and new lanes on all ramps. That includes one I use frequently—the northbound ramp on Sunol Boulevard. The southbound metering is necessary because of the morning commute. There’s rarely more than one or two vehicles that use the northbound ramp. It’s nearly inconceivable that the metering lights would ever be turned on or there would be a need for the HOV lane. There’s little, if any, land available for major residential development south of the interchange it will remain little used.
Unfortunately, CalTrans could not break out the cost of that section, but it’s a classic case of bureaucrat-think overcoming common sense.
When I posed this question, CalTrans responded through a spokeswoman with this long and detailed email.
” Ramp metering on southbound I?680, from Stoneridge Drive to Jacklin Road, was implemented in 2011 as a successful collaboration among Caltrans, Metropolitan Transportation Commission (MTC), and the local agencies who participated in the project. It had a positive effect in reducing bottlenecks on the freeway at the on?ramps and had an immediate positive effect on reducing peak period travel times. Other than the delay encountered at the ramp meters, local arterials were largely unaffected by ramp metering.
Ramp metering along the entire northbound corridor hasn’t been completed yet. Prior to the current pandemic condition, PM peak period congestion in the northbound direction lasted from the early afternoon to mid-evening, with congestion along the corridor. Some ramps operated without delay. Other ramps, such as the northern Mission Boulevard interchange, experienced delay due to existing ramp meters. However, the ramp meters attributed to reduced delay along the freeway and reduced diversion through Fremont’s streets.
Caltrans and our transportation stakeholders focus is system management and operational strategies that optimize available capacity of the existing highway infrastructure while also promoting expanded ride sharing, transit and passenger rail service. These include signal coordination on local arterials, freeway ramp metering, high occupancy/toll (or Express) lanes, and transit-oriented development near rail and transit stations.
Ramp metering can be expected to reduce travel time delays, ranging from a few minutes to as much 15 minutes, while also helping reduce collisions. Ramp metering manages the upstream demand in a corridor based on available capacity at downstream bottlenecks to prevent congestion.
If a ramp isn’t metered upstream of a freeway’s bottleneck, it would influence diversion on local streets to the unmetered ramp. As such, we need to meter all on-ramps. This is why some on-ramps have delay where it wasn’t experienced previously. In the end, though, overall delay and travel time of a freeway is reduced.
We also balance the operations of local street networks by keeping a ramp’s queue within the on-ramp and adjacent turn pockets in order to avoid gridlock on local arterials. As such, sometimes we need to sacrifice a freeway’s performance for the benefit of local traffic flow.
Before a freeway corridor’s ramp meters become operational, we will usually widen an onramp to include an high occupancy vehicle (HOV) lane. The queues on on-ramp HOV lanes are typically shorter, thus providing an incentive to ride share. On some Bay Area freeway corridors we also provide transit priority to help make transit service more predictable and reliable.”