Autobahn-Tempolimit
Overhead gantries and variable speed limits
Sometimes 120, sometimes 100, sometimes open road: on some sections the speed limit changes constantly. Behind it is a traffic control system.
Contents
What an overhead gantry is
Over heavily used Autobahn sections, metal bridges with digital displays span each lane. Technically they are called traffic control systems. Instead of a fixed sign they show a speed limit that can change at any time – or none at all, in which case the section is open. They also display warnings such as "jam", "accident" or "wet".
How it decides what applies
The system continuously evaluates measurements and switches to the appropriate limit. The main influences:
- Traffic density: sensors in the road count vehicles and measure speed. As it gets denser, the system lowers the speed so that traffic keeps flowing longer instead of tipping into a jam.
- Weather: wet, fog or ice trigger a lower limit.
- Events: for an accident, breakdown or roadworks the speed is stepped down in advance so that no one hits an obstacle unbraked.
- Time of day: at night and with little traffic many systems open the road again.
Because the system steps down ahead of time, on a controlled section you often see several falling values one after another – 130, then 100, then 80 – before the actual hazard appears.
Is the limit binding?
Yes. A speed limit shown on an overhead gantry is legally just as binding as a fixed traffic sign. Anyone exceeding it must reckon with a fine, penalty points and, depending on the amount, a driving ban – even if the system opens the road again two minutes later. If the gantry shows no limit, the advisory speed of 130 kph applies on open road.
The map shows controlled routes with a red-blue dashed line – so you know in advance where it gets changeable.
What it means for your route
For trip planning, controlled sections are the most uncertain factor: whether it is open there right now or 100 applies depends on the moment. On the map these sections are marked red-blue dashed (the other categories: blue = open, red = fixed limit, yellow = roadworks). This lets you gauge which part of your route is reliably open and which can fluctuate. For the driving time the planner treats such sections more cautiously, because the full desired speed is rarely possible there.
Frequently asked questions
What is a traffic control system?
A row of digital display panels over the Autobahn that changes the speed limit depending on traffic, weather and time of day. In Germany around 2,826 km (10.6% of the network) is equipped this way. Colloquially they are called overhead gantries.
Is a limit on the gantry binding?
Yes, just like a fixed sign. Exceeding it is penalised with a fine and penalty points, even if the display opens the road again shortly afterwards.
Why does the system show several limits in a row?
It steps down in advance so that traffic slows in stages instead of abruptly before a hazard. That is why you often see 130, then 100, then 80.
Data basis for the network share: our own analysis of the OpenStreetMap data, as of 27 July 2026. Information on how the systems work: general explanation.