Carpool Lane Congestion and RCTC's Interstate 15 Corridor Improvement Project

Southern California's carpool lanes may appear to be dated given noticeable peak hour congestion, but that is no reason to simply do away with the system. According to Caltrans, the goals of carpool lanes are to reduce congestion and improve air quality on the State Highway System.

The law states that the carpool lane is used "to stimulate and encourage the development of ways and means of relieving traffic congestion on California highways and, at the same time, to encourage individual citizens to pool their vehicular resources and thereby conserve fuel and lessen emission of air pollutants."

Dedicated lanes for high occupancy vehicles is a viable alternative, according to the state government. In many cases, such lanes are the only alternative, in meeting federal air quality conformity standards for capacity-increasing improvement projects in metropolitan areas in conjunction with improving options for alternative high occupancy vehicle travel such as expanded bus and train services and marketing campaigns to form carpools. Carpool lanes represent one approach being used in regions throughout the state to respond to growing traffic congestion, declining mobility level, air quality and environmental concerns.

Yes, there are some corridors where the carpool lane may be lightly used during some hours. We've brought our views into the court of public opinion earlier this week on this one.

Many commuters sold on ridesharing

Those principles and benefits of carpool lanes are all good, and many commuters were sold on that notion. Guess what? Combined with the Inland Empire population growth, the carpool lanes are now jammed too during the rush hour. Under the federal law, carpool lanes are officially congested when the high occupancy vehicles in these lanes fail to maintain a minimum average operating speed of 45 miles per hour 90 percent of the time over a 180-day period during the morning or afternoon peak hours.

There have been claims that solo hybrids and electric cars are contributing to the chaos. There are some who are demanding that the exemption be abolished. Caltrans believes the state's rising population–and not solo clean vehicle access–is the primary reason for congestion in the carpool lanes. “More people are driving more cars longer distances. Our research shows that vehicle miles traveled increased faster than population growth," according to Caltrans' Chief of Traffic Operations Robert Copp. "So, with population increases, we get more traffic, more congestion." That may be true, but placing solo hybrid restrictions could be one solution to explore given that they are not really high occupancy vehicles. Restricting such access in congested areas is not the cure-all solution, but it would certainly help. The reality is that it probably won't be much longer until the majority of cars would be considered clean as more hybrids and electrics are introduced in the marketplace and prices come down.

Speaking of solo's, the other exempted vehicles are motorcycles. Should they too be restricted? Positively not. Motorcycles are considered a high occupancy vehicle simply due to safety and their small size. If a motorcycle is stuck in the general purpose lanes, that makes the roadway more hazardous. One corridor does restrict motorcycle access to its high occupancy vehicle lanes, the 91 Express Lanes. They must have a FasTrak transponder and hop into the 3+ lane. Motorcycles should be exempted from needing to register for a FasTrak transponder and pay tolls during the PM rush hour, period. There is no excuse to motorcycle safety. Automated enforcement systems can certainly detect these high occupancy vehicles.

Combating Carpool Lane Congestion

Moving forward, Caltrans will explore several strategies to reduce carpool lane congestion, including:
  • Adjusting hours of HOV operation
  • Modifying vehicle entrance and exit points in HOV lanes
  • Increasing enforcement by the California Highway Patrol, and
  • Limiting hybrid access in congested areas.
Identifying bottlenecks and the modification of access points which could include the addition a transitional weave lane certainly should be looked at by traffic engineers. There may be cases where carpool congestion is caused by a bottleneck. That's why we're keeping a close watch on the 91 Express Lane extension and the bottleneck along the I-15 south at El Cerrito Road where the highway goes to three lanes with no high occupancy lane.

There have also been local discussions of changing the occupancy requirement for carpool from 2 to 3 during congested periods. That should be looked at on a corridor-by-corridor basis by traffic engineers. We understand that such a change will be a bit chaotic at first as 2-person carpools are displaced, but strong marketing campaigns to form 3+ carpools and plans implement all day transit service should be able to offset this issue. Long term plans may include doubling the capacity so that there are two carpool lanes in each direction. The I-15 Express Lane facility in San Diego County is a prime example.

Model high occupancy vehicle infrastructure: San Diego County I-15 Express Lanes

In San Diego County, the I-15 Express Lanes corridor between Escondido and San Diego has been nationally recognized for its innovative design. It is the first section of a regional system of interconnected Express Lanes. It fosters public transit with the presence of bus infrastructure. It encourages shared ridership with park & ride lots. There's no toll for 2+ carpools and vanpools, buses, and motorcycles. They do not have to preregister ahead of time or mount a transponder. They can get on for free and go! Intelligence-driven enforcement combined with heavy fines combats carpool and toll payment cheating. Starting in 2014, the corridor will offer an all day express bus rapid transit route. This multi-modal high occupancy toll lane facility features:
  • Dual 2+ carpool lanes in each direction with the option of solo drivers to buy their way in with a FasTrak under real-time marketplace tolls. Much of the corridor also features a movable barrier where the number of carpool lanes in each direction can be adjusted easily. Under special circumstances, the barrier could be moved where one direction of the corridor would have 3 carpool lanes, the other would have 1.
  • More than 20 access points that give travelers a wide range of options of where to enter or exit the lanes. 
  • Direct access ramps that allow travelers to enter the Express Lanes from surface streets. New and improved transit stations are located less than a few blocks from these ramps, thus providing the bus transit infrastructure for high speed express bus services both from public agencies and the private sector.
  • Robust bus transit stations less than a few blocks from the corridor: Unlike LA's I-110 Harbor Transitway where the transit stations were placed in the freeway median, the stations are placed on either side of the freeway, thus making non vehicular access more pedestrian and bicycle friendly. Speaking of the notion of placing transit stations within the median of the freeway, such proposals generally must be discouraged. Getting to stops is hard enough. Patrons are often required to bridge over or under several lanes of rushing traffic. Once they are finally on the platform, the environment is chaotic. Cars may be whizzing by at high speeds in both directions, producing noise and unhealthful air around the station. That's why it's better to place the transit hubs on either side of the freeway.
Concept: What a direct access ramp with supporting bus infrastructure from San Diego's I-15 Express Lanes may look like if replicated in Temecula. An extension of Bedford Court serves as the direct access ramp. Numerous casino buses, private carpools and future public express buses would utilize it. A transit station on the opposite side of the freeway would cater to connecting RTA buses and potential local high speed rail toward Los Angeles to the north and San Diego to the south. A gateway into the Santa Margarita Ecological Reserve would also support the transit station and serve as a tourist stop. View map.
Could the Inland Empire use robust transit infrastructure like this? Let's see what our folks at the Riverside County Transportation Commission have planned.

Riverside County: Interstate 15 Corridor Improvement Project

The Riverside County Transportation Commission's Interstate 15 Corridor Improvement Project was recently reevaluated, right-sized, and re-prioritized as it emerges from its original plan of a 43.5 mile corridor improvement, to a more focused 14.6 mile stretch of tolled express lanes running North from Cajalco Road in Corona to State Route 60 (SR-60). The original proposal was to run the HOT lanes between SR-60 and SR-74 in Lake Elsinore and to build carpool lanes between SR-74 and the I-215 in Murrieta. Because of predicted growth in Temecula, we've advocated for the carpool lanes to be dual and to run through to San Diego County where it would seamlessly link with the I-15 Express Lanes. Under the current political and economic climate, that will not happen anytime soon; so prepare for more bottleneck shifting.

According to RCTC, the project has undergone the reevaluation of its project limits in order to deliver a project that could be constructed in this economic recovery period. The project originally was relying, in part, on local Measure A funding, the half-cent sales tax dedicated to County Transportation, for a large portion of its funding source.

Concept: Dual high occupancy express lanes along the I-15 freeway just north of Cajalco Road which supports free non-transponder carpooling complete with infrastructure to support future rapid express buses and private sector intercity coaches like Greyhound. The access point pictured is actually officially proposed by the Riverside County Transportation Commission as part of a scaled-down version of the I-15 tolled express lane project. Also pictured to the right is infill marketplace job growth at the Corona Crossings area.
When the Measure A funding endured multiple years of unanticipated downturn, the I-15 CIP was evaluated for what could feasibly be built that would bring maximum benefit to the public. RCTC was therefore forced to downsize the I-15 Project which is now focused on the highest traffic impact areas within the corridor.

No more excuse making

We will continue to hold the state accountable for supporting policies that would entice the local marketplace to grow and for getting our transportation infrastructure to a point of where it needs to be and county officials should think likewise and pass resolutions to demand the state to stop misspending our money. Wasteful government spending of our transportation money positively should not be tolerated. With carpool demands high and growth on the way for the corridor, the I-15 needs robust infrastructure to support the high occupancy vehicle traffic so it does not become the next 91 Freeway Corona Crawl. The corridor needs to mimic San Diego County's I-15 Express Lane system with bus transit infrastructure and usage policies that support free non-transponder carpooling. Charging mandatory tolls and transponder preregistration on carpoolers which drives non-registered HOV's out of the express lanes should not be a substitute. The state simply has no excuse for this downsizing.


  1. Would like to see your group represented at future T-NOW meetings. Visit for meeting details.

    1. Thank you for the invite. Please contact our organization's office and we can set up either an in-person presentation or teleconference.

      The Transit Coalition is an all volunteer organization and an independent broad based group of concerned citizens mobilized to passionately demonstrate community support for the economic development and continuing operation of improved transportation with this blog focusing on Inland Empire transportation. We do encourage our readers and contributors to address individual concerns to T-Now as this forum is vital to communicate concerns between riders, staff and the governing body.


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