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, NYC 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 NYC 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 NYC DOT’s Mobility Report and Dashboard, and their implications for future traffic volumes. Excess roadway width should be reallocated to provide walking, transit, and bicycling facilities, public open space, green cover, and/or stormwater source control measures. If financial limitations preclude capital implementation of street redesigns, the reallocation of space should still proceed with less costly operational approaches such as new pavement markings.
All roadway corners should be designed with the smallest possible radius that still accommodates the design vehicle and emergency vehicles. The default corner radius is 12 feet. However, in areas where curbside turns are necessary or larger vehicles need to be accommodated, a larger corner radius may be considered with approval from NYC DOT. In certain circumstances--for example, where there are no turns--the corner radius may be reduced to as low as 3 feet.
Pedestrian crossing distances should be minimized in all locations utilizing treatments such as Curb Extensions (i.e., neckdowns) with detectable warnings to make edge conditions clear to pedestrians with vision disabilities. Sidewalk narrowing and roadway widenings should be avoided.
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 | The SU-30 vehicle path shall remain fully within the striped lanes. At uncontrolled intersections in residential areas, the SU-30 vehicles can leave their lanes if safety isn’t compromised, based on engineering judgment. |
| FDNY (Seagrave) | Typical FDNY vehicle for many parts of the City | FDNY vehicles can utilize varied turn patterns that other vehicles cannot. |
| FDNY (Others) | In areas where the Seagrave is not in use; the largest appropriate FDNY apparatus should be utilized for analysis | Can utilize varied turn patterns that other vehicle types cannot. |
The following design vehicles should be used under specific circumstances and should be included in the swept-path analysis in addition to the SU-30 and FDNY vehicles noted above.
| Vehicle Type | Use | Notes |
|---|---|---|
| P | Standard Design Vehicles for special circumstances | The P vehicle path shall remain fully within the striped lanes at all times. Passenger vehicles should be used where P vehicle path is likely different than SU-30 path, including but not limited to offset crossings, truck aprons, roundabouts, and other traffic calming treatments. P vehicles may also be used to verify access to residential driveways. |
| DL-23 | The DL-23 can be used as a design vehicle for corridors that have restrictions in place for larger vehicles | Package delivery trucks commonly travel on city streets and have an inside turning radius of 22.5 feet and an outside turning radius of 29 feet. |
| CITY-BUS | Standard Design Vehicle for all Bus Routes | Used on all MTA and local routes. |
| A-BUS | Standard Design Vehicle for all Bus Routes that use articulated buses | CITY-BUS must also be checked for routes that support both articulated and non-articulated buses. |
| BUS-45 | Standard Design Vehicle for all Bus Routes that use express buses. | |
| S-BUS-36 | Standard Design Vehicle for locations near schools where school buses should be considered | S-BUS-36 vehicle path shall remain fully within the striped lanes. |
| WB-40 | Standard Design Vehicle for all intersecting Local Truck Routes | It is preferred that the WB-40 vehicle path remain fully within the striped lanes. At intersections, the WB-40 vehicle shall stay within its own approach lane but is not required to stay within its own receiving lane if it does not compromise safety based on engineering judgment. The WB-40 vehicle path cannot cross into oncoming lanes in any circumstances. |
| WB-50 | Standard Design Vehicle for all turns between Through Truck Routes and Local- or Through- Truck Routes | It is preferred that the WB-50 vehicle path remain fully within the striped lanes. At applicable intersections, the WB-50 vehicle shall stay within its own approach lane but is not required to stay within its own receiving lane if it does not compromise safety based on engineering judgment (*the template is excluded from the 2011 AASHTO list of vehicles but remains in NYC DOT’s Traffic Rules; may be found in 2004 AASHTO library). |
| WB-62 | These vehicles are generally illegal for use on NYC streets without a special permit, but the street design should ensure that they can physically negotiate a proposed geometry without getting stuck and negatively affecting traffic operations. | At intersections, the WB-62 vehicle is not required to stay within its own approach or receiving lane if it does not compromise safety based on engineering judgment. Design Vehicle may be used in the vicinity of industrial facilities or interstates that accommodate these tractor trailer sizes, or if oversized trucks are regularly observed near the project area. |
|
Other Maintenance & Emergency Vehicles |
On a case-by-case basis where specific locations require a particular type of vehicle or piece of equipment, e.g. bridges | The City has also moved to procure smaller maintenance vehicles for newer facilities like protected bike lanes. |
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 one-foot buffer on either side of the vehicle body envelope and a combined 6' for dual left turns that occur simultaneously
- Emergency Navigation: FDNY vehicles can navigate streets without adhering to lane designations in emergencies
Reasonable Expectation
When modeling vehicle paths, designers should reflect the reasonable expectation of driver behavior—not just what is technically feasible. For example, drivers are unlikely to make tight reverse curves, also known as an “S-curve,” that require significant steering adjustments. Similarly, where space allows, behavior tends to follow smoother, more comfortable paths with wider turns, often tracking alongside vertical objects. This behavior tends to also be true when designing elements such as tapers and Chicanes.
Additionally, swept path elements should start and end in reasonable locations along a path that reflects real world driving behavior. For instance, if a vehicle is approaching an intersection along a curve, its modeled path should follow that curve before turning—rather than starting the turn too early or from a straight-line segment.
Concurrent Movements
Special attention should be paid to how vehicles move through intersections at the same time—especially when multiple vehicles are turning together, such as opposing left turns. At intersections with complex geometry or jogged alignments, modeling adjacent through movements can help identify and prevent conflicts like sideswipes.
Generally, dual turning lanes should be analyzed using one SU-30 truck and one passenger vehicle, side-by-side. However, on truck routes, turning lanes should be analyzed using one WB-40 and one passenger car, side-by-side.
Consideration of concurrent movements can be both prohibitive and permissive. For example, turning paths—particularly for trucks and emergency vehicles—may overlap conventional bike lanes on the receiving leg of the intersection and should be evaluated for conflict. Conversely, nonconcurrent movements at signalized intersections can be separated through signal phasing, allowing swept paths to share the same space at different times. This strategy can reduce the overall footprint of the intersection without compromising safety or function.
Traffic Calming
Traffic calming elements like chicanes, aprons, and offset crossing islands often require a more nuanced and site-specific consideration of the swept path of vehicles along them. This can include using lower speeds and turns from stop in the analysis.
Emergency Access
All street designs must consider FDNY, other emergency vehicle, and sanitation vehicle access needs (e.g., for street sweeping and snow clearing). An emergency access lane may be required in designated NYC DOT Plazas or along Open Streets, Bike Boulevards and similar conditions.