Evacuation Route Time Estimator
Estimates total evacuation clearance time based on population size, vehicle occupancy, road network capacity, and route distance using traffic flow and queuing theory principles.
Formulas Used
1. Effective Evacuating Population:
Peff = P × (C / 100) × S
where P = total population, C = compliance rate (%), S = shadow evacuation factor
2. Total Vehicles:
V = Peff / O
where O = average vehicle occupancy (people/vehicle)
3. Total Road Capacity:
Q = L × q
where L = number of outbound lanes, q = lane capacity (veh/lane/hr)
4. Network Loading Time (Queuing Clearance):
Tload = V / Q [hours]
Time for all vehicles to enter and clear the road network
5. Route Travel Time:
Ttravel = D / v [hours]
where D = route distance (km), v = average speed (km/h)
6. Total Evacuation Clearance Time:
Ttotal = Tload + Ttravel
The last vehicle enters the network at Tload and arrives at the safe zone at Ttotal
7. Demand-to-Capacity Ratio:
D/C = V / (Q × Ttotal)
Assumptions & References
- Based on the macroscopic traffic flow model and queuing theory used in FHWA evacuation planning guidance.
- Shadow evacuation accounts for people outside the mandatory zone who self-evacuate voluntarily; typical factors range from 1.1 to 2.0 (FHWA, 2006).
- Lane capacity under evacuation conditions is typically 1,200–1,800 veh/lane/hr, lower than normal due to anxiety, overloaded vehicles, and unfamiliar routes (HCM 6th Edition).
- Average vehicle occupancy during evacuations is approximately 2.0–2.8 people/vehicle (FHWA Evacuation Traffic Information System studies).
- Compliance rates vary widely: 70–90% for mandatory orders, 30–60% for voluntary orders (Baker, 1991; Dow & Cutter, 1998).
- Model assumes a single bottleneck route; multiple parallel routes require proportional capacity distribution.
- Does not account for contraflow operations, staged evacuations, or time-varying demand curves.
- Travel speed reflects degraded conditions; free-flow speed on the same road would be 20–40% higher.
- References: FHWA (2006) Evacuation Traffic Information Systems; TRB HCM 6th Ed.; Wolshon et al. (2005) Review of Policies and Practices for Hurricane Evacuation.