Yosemite National Park Traffic Assessment and Road Network Capacity Study

During the peak season, congestion along Yosemite Valley roadways, which were designed nearly a century ago, typically lasts several hours a day. Limited parking or lots filled to capacity leave people resorting to parking in undesignated areas which is damaging the landscape. To improve mobility, protect resources and create a safer experience for all travelers, our network approach helped identify what was causing the issues and how to resolve them. 

The roadways within Yosemite Valley were designed in 1927 when park visitation was less than 500,000. In recent years, annual visitation has increased to nearly 5 million, creating significant congestion and safety concerns. 

The overall project goal for the National Park Service was to reduce congestion, developing context-sensitive solutions using the existing roadway network. Through a systematic modeling process, three critical bottlenecks were identified. The process of resolving these bottlenecks resulted in a suite of potential improvements that were vetted with project partners to determine the best solutions to move forward. 

To accomplish this, the team:

• Created a custom travel model based on visitor behavior and travel patterns
• Developed scenarios using feasible network and transit solutions 
• Analyzed scenarios to determine improvements for implementation
• Implemented a pilot roadway network to test and validate the recommended improvements

Our recommended improvements included providing additional capacity without road widening. By removing two-way travel and converting to a one-way configuration, the capacity of Northside Drive nearly doubles to process vehicles exiting the park during the outbound peak hours and eliminates an existing bottleneck at the Yosemite Falls crosswalk. This low-cost solution removed the primary bottleneck and eliminated the need for park rangers to direct traffic at the crosswalk during peak hours, saving the park valuable resources.

To reduce delays at intersections that lead to excessive queuing, the team identified continuous flow intersection solutions to reduce the number of decisions a driver needs to make, reducing congestion. To accomplish this, a portion of road along Stoneman Meadow was removed to eliminate stop-control. This configuration also simplifies decision-making for drivers and enhances pedestrian and bicycle connectivity and safety at the east end of the intersection. Additional non-transportation benefits include restoring the viewshed of Half Dome and the potential to reconnect the meadow.

We also introduced a less-typical contraflow circulation pattern on Sentinel Drive (vehicles drive on the “wrong” side of the road) to simplify intersections and eliminate congestion. The contraflow configuration allows for mostly uninterrupted traffic flow at the adjacent intersections, thus eliminating the bottleneck. It also enables park staff to manage the number of vehicles accessing some of the most visited portions of the park where parking becomes unavailable on the peak visitation days by redirecting them to other areas of the park with available parking capacity.

While the modeling results showed that the proposed solutions eliminated all bottlenecks at existing traffic levels with minimal queueing, before fully committing to permanent construction, the recommended improvements were deployed during the 2021 Yosemite Valley Circulation Pilot to test this configuration. Recommended improvements were installed temporarily during peak visitation from May through October 2021. Water-filled barriers and delineators were used in concert with signing and pavement marking changes to safely test the improvements. The changes were field-tested and modified to further improve the operation of the new traffic circulation system. To determine the effectiveness of the improvements, data was collected, and observations were made before and after installation. In addition, together with park management and first responders, a safety drill was conducted to assess response time for emergency vehicles. Throughout the summer, there were several days when all parking was full, but the roadway network remained clear of congestion. 

Following the summer pilot, the Yosemite Leadership Team decided to move forward with permanent construction of the recommended improvements. The permanent changes are expected to provide visitor access and resource protection consistent with park goals and management plans. 

In 2022, the team developed design and specifications for the construction of the project, which began in April 2023 and was completed in November 2023.

Ultimately, the project improves the experience for all visitors, whether traveling by car, on foot, on a bike or using the park shuttle system. These improvements reduce congestion, improve air quality, improve safety for all users and ease management of the transportation system for park staff. Another positive outcome of the project was the restoration of the viewsheds at Yosemite Falls and Half Dome.

The project earned an Outstanding Federal Planning Project Citation Award from the American Planning Association’s Federal Division in 2023 and the 2022 Transportation Awards Program Innovation and Development Excellence Award from the National Parks Service and the US Department of Transportation Federal Highway Administration.