Approximate Height at "Middle of the Road?"

[Dungrange]

On 15/03/2019 at 21:21, Bomag said:

Current minimum cross fall is 2.5% (See TD9/93); that can be from the centre or constant from one side to the other. 

 

That's correct, although it's probably worth highlighting that cross fall can be greater where the curvature of the road is sharper than normal.  TD9/93 is online at http://www.standardsforhighways.co.uk/ha/standards/dmrb/vol6/section1/td993.pdf and Table 3 is the most relevant to this discussion.  If you take a design speed of 50 kph (30 mph) as an example, any curve with a radius of more than 520 m may be designed with a camber, where the carriageway falls at 2.5% from the centre to the edge.   For curves down to radii of 360 m, it wouldn't be camber but a cross fall across the full width of the carriageway from the outside of the curve to the inside.  Tighten the radius to 255 m and the cross fall (super-elevation) should be increased to 3.5%.  Tighten the radius to 180 m and the cross-fall (super-elevation) should be increased to 5%.  Tighten the radius to 127 m and the cross fall (super-elevation) should be increased to the maximum of 7%.

 

In model form, all of this will likely equate to a difference of less than 1 mm in N gauge across the width of your traffic lanes.  It shouldn't be that noticeable, but probably worth doing.  However, as has also been pointed out, there should be a longitudinal gradient as well, although this may be as little as 0.5% (and even less on 'sag' and 'crest' curves - ie a dip and the brow of a hill.