Weight limits

This page is about the round red-ringed sign with a lorry and a tonnage on it.

Most weight limits are environmental rather than structural. A local authority makes them by Traffic Regulation Order to keep heavy vehicles off roads and structures that were never built for a steady stream of them: village high streets, weak bridges, canal crossings. The limit is aimed at routine through traffic.

That is why Blue Light Maps treats weight differently to every other restriction.

The default: emergency mode routes through them

In emergency mode, weight limits are ignored by default. If the quickest way to the incident is over a 7.5T bridge, that’s the way you get sent, with a lorry marker on the route so you know it’s there.

Emergency mode, exemption on: the route crosses the restricted bridge on Featherbed Lane rather than going round it.

You can see which way it’s set without opening anything. The Driving options row on the route panel reads ignoring weight limits or respecting weight limits.

What is never exempt

Height and width are hard blocks in every mode. A 3.2 m bridge stops a 3.5 m appliance under blue lights exactly as it does on the way back to station. Weight is the only restriction the app will drive you through.

Note

Restriction checks only run on the truck-class profiles. On a car or response car the app assumes you’ll fit, and the weight setting has no effect. See Vehicle profile.

Non-emergency mode obeys them

Switch to non-emergency and weight limits become hard blocks like everything else. The route takes the long way round, and the app marks the restrictions it steered you around so you can see why the route looks longer than it should.

The same journey in non-emergency mode: round the outside, with each limit it avoided marked on the road it applies to.

Each mark sits on the road it applies to, not on your route:

Mark	Meaning
	Routed around a weight limit. t for tonnes
	Routed around a height limit. m for metres
	Routed around a width limit
	Routed around a road carrying more than one of them. The same pin marks a limit you’re being routed across under exemption.

Tap one to see the road name and the limit itself, written the way the sign is: 7.5 t, or 3.50 m / 11'6".

Only detours that actually cost you time are marked, so a limit you’d have driven past anyway doesn’t clutter the map. The app shows at most 12 marks per route.

No exemption means no route

In non-emergency mode a weight limit closes the road outright. If the only way to your destination is over a restricted road, the route can fail to build rather than send you across it. Switch to emergency mode if you’re entitled to.

Telling it to respect a limit

Tap the marker on the route, then Respect weight limit. You get a choice rather than a single switch:

One road, or everywhere.

• Respect this weight limit. This road only. Everywhere else keeps the exemption. This is the one for the bridge your service has a local instruction about.
• Respect all weight limits. Turns the exemption off everywhere, for every route, until you switch Ignore weight restrictions back on in Driving options. Check your vehicle weight is right before you do.

The note is optional. It’s stored on the device alongside the road name and shown under that road in your list. It doesn’t go to control or to anyone else.

You still get a route

Under blue lights, a limit you’ve asked the app to respect is strongly avoided rather than blocked. If it’s genuinely the only way through you still get the route, still with the marker on it, and the place page tells you Respected — no other route found. A crew who asked us to respect a limit still needs a route, and giving them nothing is worse than giving them the road and a warning.

It survives restarts and map updates

Flagged roads are saved to the device the moment you tap. After a map update the app re-matches each one to its road by limit, position and name. If an update changes things enough that it can’t confidently re-match one, it refuses to guess: the entry is kept but stops applying, and the list shows Map updated — no longer applied, please add again.

Your flagged roads

Driving options → Respected weight limits lists every road you’ve flagged, with its note. Roads are removed there, or from the route marker itself (Stop respecting this limit).

The list is hidden while Respect all weight limits is on, because with that on every limit is already respected. Your entries are still there and come back when you turn the exemption on again.

CarPlay, Android Auto and the Windows app carry the all-or-nothing setting only. Per-road exceptions are managed on the phone.

Set your vehicle weight first

The exemption works by ignoring the limit, not by pretending you’re lighter. The moment you turn it off, for one road or everywhere, the app starts comparing posted limits against the gross weight in your vehicle profile.

The app doesn't decide what you're permitted to do

Blue Light Maps routes on the assumption that a weight limit is one an emergency vehicle may cross. That holds for most of them, bridges included: plenty of bridge TROs are written with an exemption for emergency services, on the basis that the crossings are rare. It doesn’t hold for all of them. A posted limit can also reflect what a structure will actually carry, and no exemption makes a weak bridge stronger. The app can’t tell the two apart from the map data, so the decision to cross is the driver’s, on the day, according to your service’s policy and local knowledge.