Next generation planes.

[old man emu]

Super-elevation, or "positive" camber is used where ever a path is designed to enable vehicles of any sort to change direction at speed. The extreme example is the banking of a bicycle velodrome. 

 

What most of us will encounter and have to del with is "negative" camber, where the surface of a road slopes downwards from the centre of the road to the edge. Next time you approach a roundabout in a suburban street, you will see this. If the road is wet and greasy, it is quite easy for the tail of a car to try to overtake the front.

 

I heard of a bloke on some similar forum as this who have lots of formulae dealing with things circling a central point. Can't remember who that was.

[facthunter]

I think the "wrong" inclination on roundabouts is for water drainage or else it's to deter speed. (which would be ridiculous). Plenty of times I've noticed virtually NO grip  when rain starts to fall. Perhaps oil and/or worn rubber particles.  or just too smooth a surface. In some leafy suburbs you get Guess what? Leaves and like the Myrtle ones in Tassie, are pretty slippery when wet.  Nev

[old man emu]

1 hour ago, facthunter said:

I think the "wrong" inclination on roundabouts is for water drainage or else it's to deter speed.

You are correct for the first part, but wrong for the second part. Attempting to deter speed in that was is quite ridiculous as you say. Rain on a road surface certainly reduces the amount of grip between tyres and the clean surface. And it's not clean water. The clean rain water picks up motor oils, road seal oils, dust of various types,  larger particulates such rubber. This becomes a slurry which further reduces the amount of grip beyond what a clean road simply wet with rain water would be.

 

 

[facthunter]

There's plenty of off camber corners appearing on fairly major roads and often as the corner progresses. This is not what one should expect to encounter so is a risk  liability unless signposted like any other road hazard should be and generally is.  Saying drive to suit the prevailing conditions doesn't really cut it as does not a sharp cornered hole in a 110 Kms zone. Preceding traffic in a lane will obscure it even if spacing is adequate and if you brake hard on a freeway unexpectedly you might initiate a multi vehicle pile up.. Nev

[Fliteright]

Simple answer to any reverse camber, drive to the conditions, slow down! 👍 Australia’s roads are generally crap!

[Yenn]

If you have superelevation on a roundabout it is easy to go round and round, but when you exit you are possibly going to get into a situation where you experience negative G.

Look at Qld rail and you will see many cases where the tracks have no superelevation. That must lead to extra rail and wheel wear. The tilt train is designed so that the carriage tilts inwards at the top to reduce centrifugal effect on the pasengers, but it does absolutely nothing to the wheel and rail alignment

[onetrack]

Roundabouts should essentially be flat, because vehicles are entering and leaving the roundabout, generally at four positions, sometimes even five, and with roads often at odd angles to each other.

 

The problem is semitrailers which are high (up to 4.3M legally), and unstable. So any super-elevation (also known as "crossfall" to road engineers) on the actual roundabout, to counter the cornering forces of vehicles on the roundabout, is going to adversely affect vehicles leaving the roundabout.

 

So a semitrailer turning left out of a roundabout that is super-elevated is going to have to deal with an adverse crossfall - meaning the semitrailer is already leaning to the right prior to making a left hand turn to exit the roundabout.

 

Many roads are poorly engineered because many road engineers and supervisors are lazy, and the likes of grader operators have poor operating skills.

Laser levelling on road-making equipment is now starting to help with the operator lack-of-skills problem, but it doesn't cure the problem of the roads already installed with incorrect crossfall, incorrect camber, and poor drainage.

 

My qualifications? Trained Military engineer, constructor of many hundreds of kms of roads and construction projects, earthmoving contractor for 30 yrs, earthworks supervisor, fully qualified and skilled operator of multiple types of earthmoving and construction machinery.

In Vietnam, our troop widened and reconstructed many of the old French roads, and we used to have grading competitions by laying a match horizontally in the road base material and seeing who could grade closest to it with the Cat road graders, without pulling the match out by hitting it. And these were old mechanical-lift blades, no hydraulic blades on Cat No 12 graders, back then.

[onetrack]

Oh, and the standard comeback for those who sneered at, or questioned our skills, abilities and qualifications, was - we were all Roads Scholars. 

[willedoo]

3 hours ago, onetrack said:

And these were old mechanical-lift blades, no hydraulic blades on Cat No 12 graders, back then.

The old 12E wrist breaker would be my guess. A mighty old machine, the 12E. I don't know about these days, but for a long time they were the most common station grader. Not much to go wrong with them.

[Dax]

8 hours ago, willedoo said:

The old 12E wrist breaker would be my guess. A mighty old machine, the 12E. I don't know about these days, but for a long time they were the most common station grader. Not much to go wrong with them.

I remember learning to drive a grader on one of those, trying to get the levers to go into their spots was a big hassle until learnt you have to throw them in or it was like driving a truck with no synchro and by the time I got the lever in place had to reverse and try again. Never really became a grader driver, but could do a reasonable job at levelling. Had a look at one of the new ones down here when they were doing the road across the valley from us and the council foreman is in our gun club. The operator does very little, all GPS and a/c. The easiest one I operated was a Britstand I think, which was a smaller grader and had hydraulics which made it so much easier to control and get a decent level for me.