Slowing down in the Dartford Tunnel

Aaron702

The Dartford tunnel running northbound from Kent to Essex has a 50mph speed limit with a minimum speed limit of 10mph. Most people that have ever used this dreaded crossing are aware of how awful the traffic is, but after using it a lot recently I have made an observation:
Even when traffic is medium-light, people will always slow down from 50mph to 40mph when they enter the tunnel. As soon as they exit, they speed up again. This is incredibly frustrating and no doubt adds to the congestion. Do people not realise the speed limit doesn't drop for the tunnel? Are they scared of driving in a dark, narrow lane? Can anybody enlighten me as to why this happens or if anybody else has made this observation.

EssexExile

I doubt a bit of slowing down so they feel more comfortable will cause much congestion. You should try other parts of the country where the speed limit isn't seen as a minimum speed.

boliston

I doubt the 10mph speed drop has much effect on the capacity of the road - it has been show that reducing speed can actually increase throughput in terms of vehicles per hour.

lewishardwick

The problem comes from the Lakeside exit on the Essex side of the bores. People see to think a solid white line can be crossed from right to left to try and make the exit. Poor forward planning.

This causes people to brake and slow down. With the way people follow too close they then brake. All the way back through the tunnel into Kent.

waamo

I've done this stretch regularly. As you exit it goes from 50 to 70. Often people fail to accelerate and sit in the outside lane at 50. Lorries start undertaking and it gets a bit silly.

I'm sure this adds to the congestion in the area. It does get a bit jammed up on that stretch.

TooManyPoints

Do people not realise the speed limit doesn't drop for the tunnel?

No, I expect they realise that the speed limit is the maximum that must not be exceeded rather than a target that must be achieved whatever the circumstances. When they enter the tunnel I imagine they drive at whatever speed they consider safe.

TooManyPoints

Often people fail to accelerate and sit in the outside lane at 50.

They sit in the outside lane because, as far as I can recall, there are double white lines for a considerable distance north of the tunnel. There's no reason (see above) why they should speed up to 70mph if they don't feel the need and they cannot legally move to the nearside lane.It's not their fault that the road layout prevents them from doing so. I also seem to recall that the 50mph limit lasts for a good stretch north of the tunnel anyway.

waamo

TooManyPoints wrote: »

They sit in the outside lane because, as far as I can recall, there are double white lines for a considerable distance north of the tunnel. There's no reason (see above) why they should speed up to 70mph if they don't feel the need and they cannot legally move to the nearside lane.It's not their fault that the road layout prevents them from doing so.

In my experience people sit at 50 way beyond the solid white lines. The roadworks haven't helped but it's as if they don't know the limit changes.

soolin

waamo wrote: »

I've done this stretch regularly. As you exit it goes from 50 to 70. Often people fail to accelerate and sit in the outside lane at 50. Lorries start undertaking and it gets a bit silly.

I'm sure this adds to the congestion in the area. It does get a bit jammed up on that stretch.

The stretch coming out of the tunnel in Essex has been at 50 for some years now, it doesn't change to 70 until past the A13 junction now which admittedly isn't far. The 50 stretch used to go on for longer whilst the main work was going on, and I suspect people haven't changed their driving habits.

The other side coming over the bridge remains at 60 for quite a while as well.

Le_Kirk

Not just me then? I came through last night just before the 22.00 cut-off for no fee and it was running freely. Most other times I agree, drivers seem to not want to drive at the speed limit. Also agree that continuing the 50 limit up to the A13 junction seems to serve no useful purpose. I have sat in queues going trough the tunnel at other times and then when you exit the tunnel to find no reason for the queue and miraculously one is able to drive at 50 mph again.

Nasqueron

Le_Kirk wrote: »

Not just me then? I came through last night just before the 22.00 cut-off for no fee and it was running freely. Most other times I agree, drivers seem to not want to drive at the speed limit. Also agree that continuing the 50 limit up to the A13 junction seems to serve no useful purpose. I have sat in queues going trough the tunnel at other times and then when you exit the tunnel to find no reason for the queue and miraculously one is able to drive at 50 mph again.

Note the key word highlighted here. It is not a requirement, it is a limit. Unless there is evidence that driving at say 40mph in a 50mph limit causes congestion, what they are doing is fine