Taking the racing line on the Motorway?

[6potdave]

I never experience an empty motorway so can't really comment, however I don't see any harm in it if there's nothing else there, make yourself feel a bit sporty

[otherman]

The reason for taking racing lines on a circuit is so you flatten the turn radius and you can go faster. Since motorways are designed to a speed rating of 100mph, there's certainly no need to do it for that reason.
Only the other hand, if its just because you fancy it....

[Pints]

otherman said:

Since motorways are designed to a speed rating of 100mph...

This, I did not know. Assuming what type of car? Some cars can take a bend at higher speeds than others.

[mmm-five]

We did a trip to the 'Ring a while ago, and whilst we were driving quickly on the unrestricted sections of the autobahn we still found it easy enough to stay to one lane. However one of our group was constantly drifting in and out of the lanes. When we stopped for petrol we asked him why he was doing so, and he replied "I'm just trying to hit all the apexes!".

Some of these bends were spread over 3 miles, so he'd be in lane 1 to start and over the course of the 3 miles he'd drift to lane 2, lane 3, lane 2, lane 1, etc. It wasn't even as if these were big bends, and you almost didn't even have to move the steering wheel to follow them.

Unfortunately he was serious, and we had to remind him that once we got onto some twister sections of forest/mountain road he should stay in the RHS lane otherwise he was likely to have a head on with another vehicle.

[otherman]

Pints said:

otherman said:

Since motorways are designed to a speed rating of 100mph...

This, I did not know. Assuming what type of car? Some cars can take a bend at higher speeds than others.

Motorways, and most duals, are designed with superelevation (ie, the road slopes towards the inside of the bend). On a motorway you can observe this by sitting in the middle lane and feel the way the camber varies from straight to curved sections. Without this the centripetal force caused by cornering would be resisted by the friction of you tyres only. The design is around 100mph based on standard assumptions about weight and grip - which are related factors in any case.
Where you hit a bend on a dual that is tighter than standard design you get a 'slow' or 'reduce speed' sign (you see this on tight motorway slip roads for instance, where they are built tight because of land take restrictions) and you will find a bigger cornering force than you are used to.
Of course most people don't know this, they just drive on the 'strip of tarmac'. Should I start about vertical and horizontal spiral entries? No, thought not.

[Pints]

otherman said:

Motorways, and most duals, are designed with superelevation (ie, the road slopes towards the inside of the bend). On a motorway you can observe this by sitting in the middle lane and feel the way the camber varies from straight to curved sections. Without this the centripetal force caused by cornering would be resisted by the friction of you tyres only. The design is around 100mph based on standard assumptions about weight and grip - which are related factors in any case.
Where you hit a bend on a dual that is tighter than standard design you get a 'slow' or 'reduce speed' sign (you see this on tight motorway slip roads for instance, where they are built tight because of land take restrictions) and you will find a bigger cornering force than you are used to.
Of course most people don't know this, they just drive on the 'strip of tarmac'. Should I start about vertical and horizontal spiral entries? No, thought not.

Geniunely very interesting. What are spiral entries? Anything to do with CW7?

[otherman]

Pints said:

Geniunely very interesting. What are spiral entries? Anything to do with CW7?

Hmm, don't know what CW7 is, something for you to explain to me.

Speed rated roads don't go directly from straight sections to radius bends, because if they did you'd have to make a sudden change in direction when you hit a curve. On a motorway this would be a disaster because people would wander out of lane at every change in direction.
Instead, there's a spiral transition, so the curve starts with a very long radius, and tightens in a spiral til it hits the required radius, follows this round the bend then spirals back out again. This is why you turn your wheel gradually in and out of bends.
The same thing happens on vertical curves as well so you don't get a change of weight at the top and bottom of hills - the way you do on a hump back bridge on a minor road.
The alignment gets real complicated when a turn is switching from left to right at the brow of a hill, because there are vertical and horizontal spirals and superelevation changes (which also spiral) all at the same time. Before we had computers it tooks weeks to calculate.

Edited by otherman on Sunday 15th May 13:58

[jake15919]

MC Bodge said:

Not necessary on most motorways other than the tight-ish bend on the lashed-up section of the M60 nr Stockport. It now has SPECS cameras anda 50 limit though.

If we ever get a 'no speed limits today lads' on the M60 that and the following down hill left would be most enjoyable.

[NHK244V]

well sing as motorways dont have turns all that tight what racing line ?