Mitigation Strategies

This is Stockton, CA !

Can you identify the number of freeways and highways within Stockton?

Can you find the Crosstown freeway?

Below is our analysis and suggestions regarding diesel truck emission mitigation and reconnecting the community:

Tolling

Adding Truck-only tolls or congestion pricing to the Crosstown freeway

Undergrounding

Replacing the Cross-town Freeway with an Underground Corridor

Rerouting

Rerouting Truck Traffic by replacing the crosstown freeway with a green boulevard

Tolling

As of now, heavy-duty trucks make up 6% of vehicles but cause 35% of transport NOₓ emissions in California (CARB, 2024). The visual on the left utilizes toll booth simulation technologies from the Iberia DLC and displays a barrier-based system with overhead camera tolling.

Case Studies: Success in Pollution Reduction

- Stockholm cut traffic by 30% and CO₂ by 14% in a year with congestion fees (Swedish Transport Administration, 2018).
- London’s toll zone reduced pollution by 12% and delays by 30% (Transport for London, 2020).

We feel that congestion pricing or truck only tolls can be a strong tool in helping South Stockton mitigate harmful pollution. Although it isn't our preferred solution, tolls can serve as a steppingstone to achieving the bigger goals we discuss below. As discussed above, tolls can help reduce air pollution in the region by about 12-14%. Even though it likely won't directly remove the Crosstown freeway, funds generated from these tolls could potentially used to fund one of the projects listed below.

Aimsun Modeling

What is Aimsun?

Aimsun is a traffic modeling software that takes in imported road networks and traffic data to simulate realistic traffic conditions.

How did we use it?

We used Aimsun to simulate a case if the Crosstown freeway was undergrounded and a case if the Crosstown freeway is rerouted. With these different scenarios modeled we aim to show the community the traffic related pros and cons of each solution.

What data did you use?

We used Caltrans 2022 diesel truck annual average daily traffic (AADT) for our traffic demand, and we used I-5, CA-99, the Cross-town freeway, Hammer Lane, Charter Way, and Arch Airport Road for our road network.

Undergrounding

Our undergroudning proposal would take the existing Crosstown freeway and replace it with an underground freeway tunnel. Ideally this will open up approximately 5 miles of new green/community space in place of the current freeway and will mitigate harmful emissions through tunnel ventilation systems.

Model Introduction:

Our Aimsun model for undergrounding the Crosstown freeway takes the road network shown below to simulate the volume of traffic traveling East-West on each segment of road. We developed this model to understand how traffic would flow through Stockton if there was a underground freeway and how that would be different than the rerouting case.

This model can also represent the current traffic volumes for Stockton's East-West truck traffic, under the assumption that the current Crosstown freeway and future underground freeway would maintain the same number of lanes and exits.

Above is an outline highlighting the road network we simulated for our model.

Shown here is an overhead screenshot of the modeled network in Aimsun.

Shown in the left is a video recording of the traffic simulation

Results:

Ultimately, the model shows that the highest percentage of traffic traveling East-West through Stockton is on the Crosstown freeway. The breakdown of traffic volume in descending order is as follows:

Crosstown Freeway: 66.23%
Arch Airport Road: 19.04%
Hammer Lane: 8.36%
Charter Way: 6.37%

Essentially this shows that 66.23% of the diesel trucks traveling East-West through Stockton, travel on the Crosstown freeway. This means that a majority of the truck emissions on an average day, surround the Crosstown freeway.

These estimates from our Aimsun model align with Caltrans truck AADT counts for the Crosstown Freeway, with both indicating a similar magnitude of approximately 10,000 trucks per day. Overall, this model was able to show a general simulation of the existing traffic conditions and the likely conditions for an underground freeway. This test will serve as a base to compare the next model to.

Pictured above is an outline summarizing the traffic volume results we gathered from our Aimsun model.

Pictured here is a screenshot of the simulated truck counts on the Crosstown freeway shown in Aimsun (Note: The width of a line shows the amount of vehicles traveling through that segment. Bigger line = More vehicles)

Rerouting

Our rerouting proposal would take the existing Crosstown freeway and replace it with diesel truck free green boulevard. Ideally this will reduce harmful emissions while offering some space for community redevelopment. Though one unanswered question is, where will the excess of trucks go?

Model Introduction:

Our Aimsun model for rerouting the freeway takes the road network shown below to simulate the volume of traffic traveling East-West on each segment of road. We developed this model to understand how traffic would flow through Stockton if there a key truck route (the Crosstown freeway) was removed and how that would be different than the undergrounding case. This model will also help us determine if other communities are put at risk due to increases in truck traffic.

The image above shows an outline for how the rerouted road network would look like. Highlighted in green is the new "Crosstown boulevard".

The screenshot above shows the road network we modeled in Aimsun (Note: There is no "Crosstown Blvd" in the Aimun model in order to ensure no trucks use the new green boulevard)

Shown in the left is a video recording of the traffic simulation

The simulation predicts where vehicles travel based on Caltrans truck AADT for "one day" (6am-6pm). The first half of the video shows a 2D overview of the model, while the second portion shows a 3D view of the model. The key difference in this model is that there is no longer a Crosstown freeway available for trucks to use.

Results:

By taking the average traffic volume on each of the East-West corridors, we found that the highest percentage of traffic traveling through Stockton is on Arch Airport Road. The breakdown of traffic volume in descending order is as follows:

Arch Airport Road: 69.89%
Hammer Lane: 19.62%
Charter Way: 10.49%
Crosstown Boulevard: 0%

Essentially this shows that 69.89% of the diesel trucks traveling East-West through Stockton, travel on the Arch Airport Road. This means that a majority of the truck emissions on an average day, surround the industrial region near the Airport. Although, this region is predominantly industrial, we risk over polluting this region by drastically increasing the number of trucks traveling through here daily. As for Charter Way and Hammer Lane, they also face significant increases in truck traffic which may also worsen air quality in their respective regions. Despite this, one positive outcome from this model is that seemingly all diesel truck emissions along the Crosstown Boulevard should be nonexistent.

Although there is no specific Caltrans truck AADT data to compare to these truck routes, our model's estimates align with the truck counts for our undergrounding model. Overall, this model was able to show a general simulation of the new traffic conditions for rerouting truck traffic away from the Crosstown freeway.

Pictured above is an outline summarizing the traffic volume results we gathered from our Aimsun model.

Pictured here is a screenshot of the simulated truck counts on the Arch Airport Road and Charter way, shown in Aimsun (Note: The width of a line shows the amount of vehicles traveling through that segment. Bigger line = More vehicles)

Final Analysis

Based on the two modeled scenarios and their associated traffic flows, we believe that undergrounding the freeway presents the most effective solution for mitigating harmful vehicle emissions and reconnecting the community. By placing the freeway underground, emissions can be more effectively managed through a tunnel ventilation system, such as the one studied by last year’s Crosstown Freeway group.

Our Aimsun simulations show that in the first scenario, the existing Crosstown Freeway carries approximately 66% of the East-West truck traffic. In the second scenario, the proposed "Airport Freeway" handles about 70% of that traffic. While the second scenario routes significant amounts of trucks and their emissions through a predominantly industrial area, we maintain that undergrounding offers greater long-term benefits. Tunnel ventilation systems are capable of capturing and removing significant volumes of pollutants, making this approach more effective for emission control overall.

Additionally, relocating the freeway underground would free up a large surface area, offering an opportunity to reconnect divided neighborhoods and create new green spaces for the community.

Below is a final side by side comparison of our two models:

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