Microsimulation of Emergency Evacuation in the Bear Lake Road and Wild Basin Areas of Rocky Mountain National Park

Akyildiz, Ayse; Pan, Bing; Xu, Guanhao; Gayah, Vikash; Esser, Scott; Hannon, John; Taff, Derrick; Newman, Peter

doi:10.36967/2319373

Rocky Mountain National Park faces escalating challenges from climate change-driven emergencies and increasing visitation, necessitating robust emergency preparedness. This study focuses on the highly visited and access-limited Bear Lake Road and Wild Basin areas, both of which are vulnerable due to being narrow, single-egress corridors. Our research utilized agent-based traffic microsimulations to estimate evacuation times and analyze traffic dynamics. Key assumptions included sufficient ranger staffing, compliant hikers, a conservative 2 mph hiking speed, and consistent transportation modes. Simulations were based on peak season visitor volumes, initiated at 2 PM on the busiest summer day. Fifteen scenarios were investigated, including 10 base scenarios: nine Bear Lake scenarios that combined traffic conditions from 2017, 2020, and 2021 with three exit strategies, and one Wild Basin scenario based on 2021 traffic conditions and a single exit strategy. Five additional scenarios examined illegal parking in Bear Lake, illegal parking in Wild Basin, ranger-assisted traffic control, a car accident, and road construction. For the Bear Lake Road Corridor, total evacuation times were around 6 hours, with the exit strategy being a greater influencing factor than annual traffic variations. A two-stage evacuation pattern emerged: approximately 80% of visitors departed within 2–2.5 hours, while the remaining 20% took significantly longer (3.5−4 hours) due to greater hiking distances from remote trails. Minor, intermittent congestion at specific intersections (US 36/Bear Lake Road, Bear Lake Road/Park & Ride) could be alleviated by ranger traffic control. Factors such as illegal parking, a car accident, or road construction had only marginal effects on overall evacuation duration, though illegal parking could delay the initial stage by about 15 minutes. In Wild Basin, the single-exit evacuation was longer, averaging 7 hours 18 minutes. This extended duration was attributed primarily to the widespread dispersion of hikers along longer trails. No significant congestion was observed. Across both areas, the rate at which hikers returned to trailheads was the most critical factor determining total evacuation time. Management recommendations include strategically deploying traffic control at minor congestion points, and more importantly, developing innovative strategies for rapid and widespread communication of evacuation orders to visitors along trails. While acknowledging policy considerations like the Wilderness Act, options such as enhancing cellular coverage, installing emergency call devices, or employing geofencing could significantly improve response times and visitor safety. Roadway improvements in Wild Basin are unlikely to offer substantial benefits, as hiker dispersal and communication speed are the primary constraints.

Microsimulation of Emergency Evacuation in the Bear Lake Road and Wild Basin Areas of Rocky Mountain National Park

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