Traffic Circles
Table 4: Typical Impacts of Traffic Circles on Emergency Vehicles
Bureau of Traffic Management
Portland Office of Transportation
City of Portland, Oregon
January 1996
Vehicle |
Lowest Speed (mph) | Desirable Speed (mph) |
Travel Time Delay (seconds) |
Impact Distance (feet) |
| Engine 18 | 14 | 25 | 2.8 | 261 |
| 14 | 30 | 4.3 | 489 | |
| 14 | 35 | 6.1 | 671 | |
| 14 | 40 | 8.5 | 814 | |
| Rescue 41 | 16 | 25 | 1.3 | 170 |
| 16 | 30 | 2.3 | 301 | |
| 16 | 35 | 3.1 | 467 | |
| 16 | 40 | 5.1 | 612 | |
| Squad 1 | 17 | 25 | 1.2 | 172 |
| 17 | 30 | 2.3 | 326 | |
| 17 | 35 | 3.7 | 501 | |
| 17 | 40 | 5.3 | 776 | |
| Truck 1 | 10 | 25 | 4.8 | 319 |
| 10 | 30 | 6.4 | 524 | |
| 10 | 35 | 8.4 | 749 | |
| 10 | 40 | 10.7 | 1034 | |
| Truck 4 | 11 | 25 | 4.3 | 322 |
| 11 | 30 | 6.2 | 549 | |
| 11 | 35 | 8.1 | 799 | |
| 11 | 40 | 10.3 | 1139 | |
| Truck 41 | 11 | 25 | 3.9 | 338 |
| 11 | 30 | 5.2 | 555 | |
| 11 | 35 | 7.3 | 845 | |
| 11 | 40 | 9.2 | 1255 |
Lowest Speed: This is the lowest speed a vehicle travels when navigating around a traffic circle.
Desirable Speed: This is the speed a driver might wish to travel if there were no traffic circles.
Travel Time Delay: This is the additional time required to travel to a destination due to a traffic circle's influence.
Impact Distance: This is the length of street where a given vehicle cannot be driven at the desired speed because of the traffic circle's influence.