ADUK Archive

Cars come in integers. Anything less that 2 cars is single track.

7db wrote:Cars come in integers. Anything less that 2 cars is single track.

Cars do but road users don't. The biggest things you might realistically meet coming the other way at speed are trucks and buses, so if you're in a car surely it's that anything less than 2.5 cars wide is single track?

Gareth wrote:If cars are approximately 2m wide, and a single carriageway is, in general, at least 5.5m wide, there is only room for one car in each direction plus a margin for safe passage.

A family car is normally less wide than two meters, and stands at an average of 1.7 meters. As for, "at least 5.5m wide" - at least is the operative word. The average single carriageway (with a center line) should be about six meters wide, sometimes even seven meters.

That does not even include the hard shoulder (if there is any, which there usually is) and the "soft" shoulder (verge, gravel etc) past it which often allow extra room to manuever.

Astraist wrote:

Gareth wrote:

A family car is normally less wide than two meters, and stands at an average of 1.7 meters. As for, "at least 5.5m wide" - at least is the operative word. The average single carriageway (with a center line) should be about six meters wide, sometimes even seven meters.

Not in the UK it isn't. In general only our trunk roads (and some ex trunk roads) are so wide. The majority of our rural 2 lane minor roads are not far from 5.5m, and it is commonplace to see trucks having to mount the verges when they meet. It is certainly not the norm to have enough space to physically fit 3 cars abreast.

I can think of several local 2 lane roads where overtaking is hazardous simply due to lack of width

I understood single track roads to be those where specfic passing places are necessary, whereas single lane roads allow two cars to pass without leaving the carriageway, though at low speeds as there's little spare room.

As for the road in question, I'd guess it to be 8-9m wide. Plenty of room for three-abreast (as in its former state, with a central suicide lane), but the problem is trusting other drivers to realise this and position accordingly.

I wonder whether the whole thing would be a lot safer if it were to revert to three lanes, but with the central lane alternating to be available to only one side at a time. It would stop people thoughtlessly sailing up the middle from both sides, and with sensible layout would have very little negative effect on traffic flow.

We have to judge these situations as they arise, but on that sort of road I'd be looking for safe opportunities to go through the middle.

true blue wrote:I wonder whether the whole thing would be a lot safer if it were to revert to three lanes, but with the central lane alternating to be available to only one side at a time.

Stop it. Those things are the devil's work.

true blue wrote:I wonder whether the whole thing would be a lot safer if it were to revert to three lanes, but with the central lane alternating to be available to only one side at a time. It would stop people thoughtlessly sailing up the middle from both sides, and with sensible layout would have very little negative effect on traffic flow.

Why not remove the paint altogether? Alternating priorities might actually make things worse if people start assuming that a double white line to oncoming traffic guarantees no-one will cross it. Ignoring lunatics, there are several legal exemptions for doing so. At least with 3 lanes and dashed lines theres a reminder it's quite likely you might meet an oncoming overtaker.

michael769 wrote:

Gareth wrote:In the UK the regulations (pdf) say that single carriageways less than 5.5m wide should not have a centre line (paragraph 4.6).

TSM is guidance not law. No such regulation exists.

Hi Gareth, if you're having trouble sleeping, take a look at TD27/05 of the Design Manual for Roads and Bridges. It provides the standard cross-sections for new roads - Trunk and Motorways. I think you'll find them to be a tad wider than the roads you prefer to drive on

GJD wrote:

true blue wrote:I wonder whether the whole thing would be a lot safer if it were to revert to three lanes, but with the central lane alternating to be available to only one side at a time.

Stop it. Those things are the devil's work.

2+1s as they are known within the Roads community. Being used as a low cost alternative to full dualling and full of lots of little anomalies made to make life interesting.......

Big Err wrote:2+1s as they are known within the Roads community. Being used as a low cost alternative to full dualling and full of lots of little anomalies made to make life interesting.......

My favourite bit is when your two lanes are about to drop to 1. You and the drivers around you get to race up to the pinch point all trying to be first into the single lane. The same as any end of dual carriageway bun fight really, except if you didn't win it's only two miles before you get to have another go .

The A507 was built as a two lane road. It has never had 3 lanes or an alternating 2/3 system. Overtaking through the middle is endemic.

Terry Williams wrote:The A507 was built as a two lane road. It has never had 3 lanes or an alternating 2/3 system. Overtaking through the middle is endemic.

Really? In that case, someone from the Highways Agency or the Department for Transport needs to be shot, for intentionally creating such a half-cocked road! I'd be interested to know at what period in history such roads were considered either to be common or sensible...

true blue wrote:

Terry Williams wrote:The A507 was built as a two lane road. It has never had 3 lanes or an alternating 2/3 system. Overtaking through the middle is endemic.

Really? In that case, someone from the Highways Agency or the Department for Transport needs to be shot, for intentionally creating such a half-cocked road! I'd be interested to know at what period in history such roads were considered either to be common or sensible...

There are quite a lot of them around, though - as well as the A5, parts of the A49 Shrewsbury Bypass and A46 Evesham Bypass are the same. As was the A303 Ilminster Bypass, although that was later converted to an alternating 2+1 lanes layout. I think at one time it was a recommended design standard.

PeterE wrote:There are quite a lot of them around

When you say "them", you mean roads marked out as two lanes that would be easily wide enough for three or more? I didn't think that was a particularly abnormal phenomenon either.

Can't see what the problem is. It's a road. Drive along it. Don't crash into anything . I've no particular difficulty with the idea of three abreast. Four can be managed sometimes. I love a road where you can get on with things.