What you see while navigating
While you navigate, a US-style speed limit sign sits above your current speed. When a limit applies only to trucks, the sign reads TRUCKS, so you know the number is your limit and not the one posted for cars.
If you're 5 mph or more over the limit for 4 seconds, your speed bubble turns red and Fort Route says the limit once. It doesn't keep repeating: you hear it again only when the limit changes or 2 minutes later. Warnings play only during navigation, never while you preview a route.
In a work zone where the DOT feed lists a reduced limit lower than the posted one, the sign shows WORK ZONE with that limit. Road work alerts explains which feeds Fort Route reads.
Where the limits come from
Fort Route reads the limit for each stretch of your route from the same map data its truck routing uses: OpenStreetMap's posted limits and, where mappers have added them, separate limits for heavy trucks. That gave Fort Route speed limits on about 95% of tested routes.
On top of the map data, Fort Route applies statewide truck limits set by law:
- California: 55 mph
- Washington: 60 mph
- Indiana: 65 mph on interstates
These limits matter most on the roads where cars may legally go faster than you can. Seeing the truck limit on the sign saves you from working it out from a car limit at highway speed.
When there's no sign
When Fort Route doesn't know the limit for a stretch of road, it shows no sign at all. A guessed number could be off in either direction, and a blank sign tells you plainly to go by the posted signs.
OpenStreetMap is maintained by volunteer mappers, and a mapped limit can lag behind a newly posted sign. The posted limit is the law, so follow it whenever it differs from the app.
Some speed limits are also enforced by camera. Fort Route warns you before mapped speed and red-light cameras on your route; see traffic cameras for how those alerts work and where coverage is thin.
Frequently asked questions
Does Fort Route show truck speed limits or car speed limits?
Fort Route shows the truck limit when one is known, marked TRUCKS on the sign. Truck limits come from OpenStreetMap's truck-specific limits and from statewide truck limits set by law, such as California's 55 mph. Where no truck limit is known, the sign shows the general limit for the road.
Why is there no speed limit sign on part of my route?
Fort Route doesn't have a limit for that stretch, so it shows nothing rather than guess. Go by the posted signs there.
How often will Fort Route warn me about speeding?
Fort Route warns you once for a given limit, after you've been 5 mph or more over it for 4 seconds. Your speed bubble turns red at the same time. You hear the limit again only when it changes or 2 minutes later.
How accurate are the speed limits?
The limits are as accurate as the OpenStreetMap data behind them, which can lag behind a newly posted sign. Fort Route found limits on about 95% of tested routes, and the posted limit always wins when the two disagree.