blckwall tunnel average speed check? dud camera or real?

londonTiger

Whenever I drive southbound, everyone is doing around 40mph on the downward slope and then 35mph on the upward slope. But the speed limit is 30mph and supposedly moniotered using average speed checks.

I stick to the 30 limit, as I sped through a few times there at 40 and panicked myself that I might have a speeding ticket through the post.

But I feel like a bit of a numpty when I do 30. Because there's a backlog of people behind me and the drivers on the other lane are slowly passing me.

I dont think anyone is getting speeding tickets driving fast down there, I think if people were getting tickets they would start to drive slower - it only takes 2 drivers to slow down the entire que of cars, so just a few people getting tickets would have a noticable affect on the average speed there.

So with that in mind has anyone received tickets?

keith1950

Hi, I cannot comment specifically on the Blackwell tunnel however, whereas the police usually use a threshold of 10%+ 2mph ( 35mph in 30mph limit ), quite often these sort of sites use a higher limit so it could be 40mph.

It then takes away any doubt ......if your doing 40mph in a 30mph limit you deserve a ticket .

Browntoa

90% of the time you cannot go faster than 10mph through there

Too much traffic !

vikingaero

35mph should be OK as your speedo will overread slightly. Your real speed will be closer to 30-33mph depending on the car you have.

Buzby

The Clyde Tunnel also has a 30mph (plus 8mph minimum), I recall a story in the local press celebrating its 50th Anniversary, and the comment that nobody had been done speeding thought it.

When flowing normally, 45mph and above is easily possible and I've even been overtaken at 40 with no issues. I would imagine rather than restricting movement they're happy to see it flow. (Unless TFL need the money?).

neilmcl

Where are the cameras sited?

Cornucopia

Went through there last weekend. The cameras are on the Northbound side only.

The Southbound side used to have a 40mph limit. Nothing has physically changed so the route is arguably safe for that speed.

londonTiger

vikingaero wrote: »

35mph should be OK as your speedo will overread slightly. Your real speed will be closer to 30-33mph depending on the car you have.

it's not that bad, I've checked the accuracy of mine. If I hold 40mph on my speedo on a dual carriageway I get actual speed of between 39 to 40mph (according to GPS).

Idiophreak

Average speed cameras, by their nature, are nowhere near as accurate as GATSOs..they have to account for people changing lanes, moving around on the road etc - so they'll have really quite a high limit set relative to the actual speed limit.

londonTiger

Idiophreak wrote: »

Average speed cameras, by their nature, are nowhere near as accurate as GATSOs..they have to account for people changing lanes, moving around on the road etc - so they'll have really quite a high limit set relative to the actual speed limit.

No, they can inaccurately under read due to traffic, lane changes etc. But they can never innacureately over read. They're watching out for people going over the speed limit so it should not be a problem catching speeders.

speed = distance/over time

distance is predefined. Two time stamps are required, one going in one going out. It should be dead easy to spot those who are blazing through the tunnel (as does happen). It's a dual carriageway before and after the tunnel. Many people just carry on the speeds they were doing in the carriageway.

neilmcl

Idiophreak wrote: »

Average speed cameras, by their nature, are nowhere near as accurate as GATSOs..they have to account for people changing lanes, moving around on the road etc - so they'll have really quite a high limit set relative to the actual speed limit.

Evidence for this?