Worldwide, an estimated 1 billion drivers use digital maps daily.1 Routing is based on certain algorithms and road function classes to expedite travel times by avoiding delays, traffic congestion, or other disruptions. On-demand navigation is so ubiquitous that drivers rarely give it a second thought.
However, regardless of following the best routes as mapped by any popular app, drivers are still beholden to speed limits — a largely inescapable factor that impacts time on the road.
Posted speed limit databases are instrumental in providing this information to end-users, but it’s up to app developers and GIS professionals to determine and access the speed limit database suitable for their use case.
Who Determines Speed Limits?
In the United States, speed limit jurisdiction falls under the purview of the individual state governments but their legislation isn’t arbitrary. The U.S. Department of Transportation Federal Highway Administration provides the general structure — defining statutory, posted, and special conditions speed limits to bring consensus about manageable speeds based on road types and help refine law enforcement jurisdiction.
While the federal ranges are accepted — such as 25 mph in residential and school districts, 55 mph on rural highways, and 70 mph on interstate highways2 — the guidelines aren’t intended to account for real-time scenarios drivers encounter daily.
4 Popular Choices in Posted Speed Limit Databases
Posted speed limit databases are literally built to be responsive and granular. To ensure drivers get accurate information when needed, app developers and GIS professionals must be confident in their posted speed limit database and the data contained therein. Among the most popular choices include:
- Google Roads API: Available to Google customers with Asset Tracking licenses, the Google Roads API Speed Limit feature uses accumulated data to return posted speed limits for specific road segments.
- HERE Speed Limit Data: Detailed datasets enrich applications so drivers are readily advised against violation of traffic restrictions and informed of maximum posted road speeds. HERE offers speed limit data whether you are accessing the information via their mapping APIs or licensing traditional GIS map data.
- OpenStreetMap API: Speed limit data is available but not readily accessible in this crowd-sourced option. The formulaic approach to appropriately coding speed limits and entering values to determine maximum speed limits (or, maxspeed) for roadway segments and vehicle types can be time-consuming, and also complicated by sometimes absent values leaving developers to estimate speed limits based on road type alone.
- TomTom MultiNet: This robust map data solution incorporates actual speed limit data by street segment and road function class into its Route, Find & Display format.
Each database offers use case benefits and lesser degrees of drawbacks. Developer preference plays a role but not to the exclusion of the best fit for the application. HERE and TomTom are versatile speed limit databases and other map data solutions. Reach out to ADCi to discuss how they can address your needs.
1IEEE Spectrum, Your Navigation App Is Making Traffic Unmanageable, September 19, 2019
2U.S. Federal Highway Administration, Reference Materials - Safety | Federal Highway Administration, Undated