Highway Evacuations in Selected Metropolitan Areas: Assessment of Impediments
INRIX® National Traffic Scorecard 2009
Currently, no Colorado DOT (CDOT) plan specific to evacuation operations exists. However, individual communities develop and maintain evacuation plans to address events such as fires or floods. The North Central Region, which is comprised of 10 counties in the Denver metropolitan area, has begun to develop an evacuation plan that covers a 25-mile radius outside the Denver metropolitan area. The plan is titled the North Central Region Mass Evacuation Plan (draft-June 2008). This plan is only focused on evacuation of some parts of the metro area and not all areas at one time. An interviewee noted that the reason an evacuation plan was developed for the North Central Region was because it is part of the DHS UASI, which requires that 75 UASI areas develop an evacuation plan.
Top Highway Impediments
The interviewees reported that the following impediments would frustrate large-scale, mass evacuation efforts in the Denver and the North Central Region of Colorado:
Top Highway Impediments
- No Evacuation Plan
- No Evacuation Routes Identified
- No Lane Assignments for Emergency Services
- Infrastructure Limitations
- Traffic Flow Analysis on Evacuation Routes
- Weather Hindrances
- No Evacuation Plan - Interviewees noted that since there is no final plan, there are no elements that would be identified in a plan, such as evacuation routes and signs or directional indicators to identify evacuation routes. One respondent stated that the next step for the North Central Region is to hold a workshop and to start working through some of the more specific issues identified in the North Central Region Mass Evacuation Plan, such as the risk-based areas of exit. This workshop is scheduled for May 2010. The plan does not address contraflow operations.
- No Evacuation Routes Identified - No evacuation routes are identified.
- No Lane Assignments for Emergency Services - Denver authorities maintain no designated lane assignments for the movement of evacuees and emergency services equipment.
- Infrastructure Limitations - Respondents noted that the Denver area has only one major highway running north to south (I-25) and one running east to west (I-70). These highways have significant restrictions in the number of lanes, curves and choke points which severely affect traffic throughput. These two highways are the only major roads which exit the metro area. Several other smaller highways feed these two which will also increase traffic volume in the event of an evacuation. Those interviewed indicated that the biggest limitation is that all the routes out of Denver turn into two lanes outside the metropolitan area. An evacuation study that collected additional information regarding system choke points would aid evacuation planning and operations.
- Traffic Flow Analysis on Evacuation Routes - During the interview, it was noted that one analysis that has not been done is a traffic flow analysis to determine the maximum capacity of highway infrastructure, particularly on I-25 and I-70 and some of the arterials that would support an evacuation. Most of those interviewed do not believe that any time-model studies exist on the capacity of infrastructure that might be used for an evacuation. These studies, for example would consider how long it would take to move 50,000 people during off-peak and peak hours. However, one respondent associated with the North Central Region planning effort noted that their traffic management committee conducted a general analysis for all of the major routes, looking at the different levels of service and capacities. The draft North Central Region Plan includes a diagram showing the city and its major highways including contraflow lanes leaving the city. The committee made an assumption that inside the C-470 loop there is not a lot that can be done to control traffic movement.
- Weather Hindrances - Depending on the time of year the incident occurs, another impediment may be weather-related, specifically snow, rain, or flooding. Officials noted that one assumption about the potential for evacuating populations from Denver is there are no events that could occur within the State of Colorado that would give enough advance notice to execute an evacuation. As a result, instead of evacuating to escape harm's way, officials may evacuate to mitigate any threats to the population, such as a chemical spill or some type of nuclear device detonation where there is little to no notice.