Roadway Design: Vehicle Target Speed
Streets should be designed with target speeds and speed limits appropriate to their surrounding uses and desired role in the vehicular network. The citywide speed limit is 25 mph, except where otherwise noted.
Following the enactment of Sammy’s Law in May 2024, DOT is now authorized to reduce speed limits to 20 MPH on most streets and to 10 MPH on select streets undergoing safety-related redesigns. However, the speed limit for streets with three or more travel lanes in the same direction outside of Manhattan will remain 25 mph. For more information, review DOT’s Regional Slow Zones.
Roadway Design: Width, Corner Radii, and Crossing Distance
The roadway — the portion of a street ordinarily used by motor vehicles and cyclists, exclusive of the sidewalk — should be designed to be the minimum possible width, with the minimum number of lanes, that safely and cost-effectively allow for the travel of motor vehicles and cyclists. Narrower roadways minimize pedestrian crossing distances, encourage safe driving behavior, and reduce impermeable, heat-absorbing asphalt coverage.
Roadway modifications should be designed for the expected traffic volumes in the year that construction will be complete. Consider recent trends in traffic and mode choice — as documented in DOT’s Mobility Report and Dashboard — and their implications for future traffic volumes. Excess roadway width should be reallocated for walking, transit, cycling, open space, green cover, and/or stormwater control. If capital improvements are not feasible, use operational treatments such as pavement markings.
To reduce pedestrian crossing distances and slow turning vehicles, design roadway corners with the smallest possible radius that accommodates design and emergency vehicles. Where no turns exist, radius may be as low as 3 feet. The default corner radius is 12 feet, but larger may be allowed with DOT approval in special cases.
Minimize crossing distances using treatments like Curb Extensions with detectable warnings for pedestrians with vision impairments. Avoid sidewalk narrowing and roadway widening.
Vehicle Swept Path Analysis
Vehicle Swept Path Analysis is a key part of the geometric design process for intersections, curb cuts, and right-of-way planning. It ensures vehicles of all sizes can maneuver safely without conflicting with other users. Simulations help determine placement for elements like curb extensions and pedestrian islands.
The typical design vehicle is a single-unit truck (SU-30) with a 30-foot turning radius. Larger vehicles may be considered in special contexts like bus or truck routes. Design vehicles should never exceed NYC’s legal commercial vehicle limits.
Design Vehicle Types
All projects should include a swept-path analysis with the SU-30 and the appropriate FDNY vehicles.
| Vehicle Type |
Use |
Notes |
|---|
| SU-30 |
Standard Design Vehicle for ALL Streets |
Path must stay fully within striped lanes. At uncontrolled intersections in residential areas, can leave lane if safety is not compromised. |
| FDNY (Seagrave) |
Typical FDNY vehicle |
Can make turning movements that other vehicles cannot. |
| FDNY (Others) |
Used where Seagrave is not standard |
Use largest appropriate FDNY apparatus; also allows varied movements. |
The following vehicles are used under specific conditions and in addition to the vehicles above:
| Vehicle Type |
Use |
Notes |
|---|
| P |
Passenger vehicle |
Must remain in striped lanes. Use for offset crossings, truck aprons, and verifying access to driveways. |
| DL-23 |
Delivery truck |
Used in corridors with larger vehicle restrictions. Inside radius 22.5', outside 29'. |
| CITY-BUS |
Standard bus |
Used on all MTA and local routes. |
| A-BUS |
Articulated bus |
Use on articulated routes; also check CITY-BUS access. |
| BUS-45 |
Express bus |
Used on express routes. |
| S-BUS-36 |
School bus |
Path must stay fully within lanes. Use near schools. |
| WB-40 |
Local truck |
Preferred to stay within striped lanes; must stay within approach lane; cannot enter oncoming traffic. |
| WB-50 |
Truck route connector |
May leave receiving lane when safe. Still governed by NYC Traffic Rules. |
| WB-62 |
Oversized truck |
Usually illegal without permit. Used near industrial zones or interstates. Must not block or get stuck in street geometry. |
|
Other Maintenance & Emergency Vehicles
|
Specialized access needs |
Used for bridges, snowplows, smaller bike-lane sweepers, etc. |
Speed
6 mph for turns; use target corridor speed for through movements.
Placement
Vehicles should be aligned to the centerline of the approach lane and must snap to the centerline of the receiving lane after turning.
Buffer Zone
- Add 1' buffer on each side of the vehicle envelope
- Add 6' total for dual left turns occurring simultaneously
- FDNY vehicles can ignore lane markings in emergencies
Reasonable Expectation
Model vehicle paths based on realistic driver behavior. Avoid S-curves and tight zigzags. Turns should follow natural curves.
Concurrent Movements
Check for conflicts when vehicles turn at the same time. SU-30 and passenger vehicles should be modeled together. At signalized intersections, consider separate phasing to reduce conflicts.
Traffic Calming
Chicanes, aprons, and offset islands may require special swept path studies. Use lower speeds or turning-from-stop analysis.
Emergency Access
All designs must account for FDNY, emergency, and sanitation vehicle access. Provide dedicated lanes where needed, including on Plazas, Open Streets, and Bike Boulevards.