When road construction disrupts normal traffic flow, detour planning becomes essential, not just for maintaining mobility, but for ensuring safety. Poorly planned detours can lead to driver confusion, increased crash risk, and headaches for both motorists and local officials. Safe detour planning isn’t just a courtesy, it’s a responsibility. Here’s how highway departments and project managers can do it right.
Start with a Traffic Impact Analysis
Before setting up a detour, perform a traffic impact analysis. Understand how many vehicles use the affected road, what types (cars, trucks, school buses, emergency vehicles), and during which times. This data will guide whether a simple detour will suffice or if advanced planning is needed, especially in urban or high-volume areas.
Choose Routes that Can Handle the Load
Detours should not simply redirect traffic to the nearest available road. Instead, they should account for:
- Roadway capacity – Can the detour road handle the increased traffic volume?
- Pavement condition – Is it suitable for heavy trucks or buses?
- Bridge limits and weight restrictions
- Sharp turns or low visibility areas
Avoid sending large trucks through narrow residential streets or school zones. The chosen route should be structurally sound, safe, and appropriate for the detoured traffic.
Follow MUTCD Guidelines
The Manual on Uniform Traffic Control Devices (MUTCD) provides standards for signage, barricades, and detour layouts. Compliance ensures consistency and legality, and helps protect municipalities from liability.
Key signage includes:
- Advance warning signs (e.g., “Road Closed Ahead”)
- Detour arrows and route markers
- Clear notice of closures for local traffic or access only
Signs must be highly visible, placed far enough in advance for drivers to react, and maintained throughout the project.
Maintain Emergency and Local Access
Detour plans should always include coordination with:
- Emergency services
- Public transportation
- School districts
- Garbage and utility services
Local access for residents and businesses should be preserved wherever possible. Posting detour maps on town websites or sending direct notices helps reduce frustration and confusion.
Light the Way at Night
Detours that will be active overnight or in low-light conditions must be well-lit and use reflective materials on all signage and barricades. Solar-powered arrow boards or flashing beacons can be a worthwhile investment for longer-term projects.
Monitor and Adjust
Conditions change, therefore detour plans should too. Once the detour is in place, monitor its performance. Are vehicles backing up? Are drivers bypassing signs or ignoring restrictions? Regular check-ins allow you to tweak signage placement or even reroute traffic if necessary.
Communicate with the Public
Informing the public in advance can make or break the success of a detour. Use:
- Local news outlets
- Social media and town websites
- Road signage posted well in advance
- GPS mapping updates (when possible)
Clear communication reduces confusion, helps traffic flow smoothly, and builds public trust.
Safe detour planning is more than a logistical hurdle. It’s an opportunity to demonstrate foresight and professionalism. By prioritizing safety, communication, and adaptability, highway departments can minimize disruption and keep their projects—and the public—moving forward safely.