Everyone wants to reach their travel destination safely. Safe travel speeds support this goal in two ways:
- Safe speeds lower the risk of crashes
- When crashes occur, safe speeds make it less likely that people are killed or seriously injured
Unsafe speeds are a factor in about half of deadly crashes in Portland. This is why speed is a focus of the city's Vision Zero Action Plan, which aims to eliminate deaths and serious injuries from Portland streets by 2025.
Small changes in speed have big impacts
As people travel faster, the risk of death or serious injury rises dramatically. As noted in Portland's Vision Zero Action Plan and the diagram below, a person walking struck by a person driving 40 mph is eight times more likely to die than one struck by a person driving at 20 mph.
What makes a 'safe speed'
In urban places such as Portland, safe speeds must account for people traveling in different ways: walking, driving, using mobility devices, biking and skateboarding. It is important to consider people traveling outside of motor vehicles because they are not protected from the impact of crashes. This is why Portland and other cities refer to people traveling outside of motor vehicles as vulnerable users.
PBOT uses the following principles to identify safe speed limits:
- Less physical separation between people driving and vulnerable users supports a lower speed limit. Sidewalks and protected bike lanes are examples of physical separation between people driving and vulnerable users (see photo below).
- Injury crashes are an indicator that speed limits may be too high
- PBOT may request speed limit reductions even when street design stays the same. While street design can help people drive at safe speeds, adjustments to speed limits alone can still support safety.
- The 85th percentile method is not supported by evidence and is not part of PBOT practice. The 85th percentile method sets speed limits based on the speed at which 85 percent of people drive at or below on a street. The Federal Highway Administration offers a detailed guide on the 85th percentile method and other speed setting approaches.
SW Moody Avenue uses physical separation to help keep people safe.
4 ways PBOT can request speed limit changes
In order to change a speed limit, the Portland Bureau of Transportation must send a request to the Oregon Department of Transportation. The request and steps involved depend on the type of street involved and the desired speed limit:
|Request type||Eligible streets||Details and examples|
|1. "Alternative"||Non-arterial streets with speed limits above 25 mph||Excludes arterial streets but includes many collectors. Results in an updated "speed zone order" held by the state; you can look up speed zone orders for specific streets online. Authorized by ORS 810.180.
Example: Reduction from 35 to 30 mph, SE 92nd Ave., in 2017
|2. "Traditional"||All streets||Required on arterial streets except on sections eligible for business district statutory speed limits. Requests are typically slow and resource-intensive. Uses multiple factors to determine speed limits, including crash history, "roadside culture," traffic volumes, and roadway alignment, width and surface. Results in an updated "speed zone order" held by the state; you can look up speed zone orders for specific streets online. Authorized by ORS 810.180.
Example: Reduction from 40 to 35 mph, SE Stark St., 2017
|3. Statutory||Streets with a speed limit specified by law (see table below)||Requests are relatively simple and fast. Applies to alleys and narrow streets, school zones, residence districts (except arterials), and business districts; see details in the table below. Authorized by ORS 811.111.
Example: Reduction from 25 to 20 mph, NE Alberta St., 2017
|4. Special clauses||• Low-traffic neighborhood greenways
• Certain residential streets
|Allows for 5 mph below statutory speed limits on certain streets. Authorized by ORS 810.180.
Example: Reduction from 25 to 20 mph, NE Rodney Ave., 2015
ORS 811.111 describes speed limits deemed appropriate for specific street types.
Many streets in Portland have speed limits higher than statutory speed limits because they have speed zone orders. PBOT must request that a speed zone order be rescinded in order for a statutory speed limit to take effect on an eligible street (request type 3 in the table above).
|Narrow residential roadway||15||“Located in a residence district and not more than 18 feet wide at any point between two intersections or between an intersection and the end of the roadway”|
|Business district||20||Includes arterial streets. ORS 801.170 defines a business district as "the territory contiguous to a highway when 50 percent or more of the frontage thereon for a distance of 600 feet or more on one side, or 300 feet or more on both sides, is occupied by buildings used for business.”|
|School zone||20||Must meet school zone requirements|
|Residence district||25*||Excludes arterial streets. ORS 801.430 defines a residence district as "territory not comprising a business district that is contiguous to a highway that: (1) Has access to property occupied primarily by multifamily dwellings; or (2) Has an average of 150 feet or less between accesses or approaches to: (a) Dwellings, churches, public parks within cities or other residential service facilities; or (b) Dwellings and buildings used for business."|
|*2017 state legislature granted Portland authority to drop residential speed limits to 20 mph|
PBOT has worked with ODOT to obtain permission to use an alternative method to investigate streets for new speed limits. This method, implemented in late 2016, allows PBOT to request new speed limits using less staff time. The new speed request process also places greater emphasis on vulnerable users and the risk of a future crash.
Under the alternative process, PBOT uses the following general guidelines when requesting new speed limits on eligible streets:
- 40 mph maximum on streets without a center median barrier and edge clear zone, and where people walking and biking are physically protected.
- 30 mph maximum on streets with busy intersections experiencing high crashes, on streets with sidewalks or shoulders next to travel lanes, and on streets with bike lanes next to motor vehicle lanes.
- 20 mph maximum on shared space streets (driving, biking and walking) that do not meet school, business or neighborhood greenways statute for 20 mph.
The alternative guidelines do not apply to federally classified arterial streets and highways, or on any other streets with speed limits less than 25 mph.
Streets that are eligible for changes under the alternative request process (shown in orange):
You can view a map of arterial streets through ODOT's map tool:
- Go to http://gis.odot.state.or.us/transgis/
- In the layer catalog on the left, select "classifications"
- Under classifications, select "Federal Functional Class - State" and "Federal Functional Class - Non-State"
- Click "apply"
- Zoom to Portland. Click "legend." Streets that must use the standard ODOT speed limit request process include all interstates and arterials, except for segments located in business districts.
Many ways to support safe speeds
The City of Portland standard is to design streets and street retrofits to the posted speed limit to ensure that all design elements of the street convey to drivers the appropriate speed. This is different from a traditional approach of designing streets to actual auto speeds, regardless of the posted speed limit.
In addition to signage, PBOT has many street design tools available to align speed limits with actual driving speeds. These tools include lane widths, traffic signal timing, curb extensions, and landscaping. In addition, police officers and speed safety cameras help align speed limits with actual travel speeds.
Portland's Vision Zero Action Plan includes three actions to support safe speeds:
- Pilot speed safety cameras on four high crash corridors in the first two years; expand program to additional high crash corridors following the pilot
- Gain local authority for speed reduction on City of Portland streets; prioritize setting safe speed limits in the High Crash Network
- Improve street design to support safe speeds in conjunction with posted speed reduction on four to six streets (not including SD.1 improvements) annually in the High Crash Network, prioritizing improvements in and engaging with Communities of Concern
PBOT will track and report progress on Vision Zero actions and results on an annual basis.