some day soon (heh, ok it won't really be soon) I'll start a thread on road design since I've found many interesting things lately..
but till then, since you are at that perfect spot for these tips, here they are =)
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there are a few subtle things goin on in most roads that many people don't see when you are driving, around every day ..
- road crown - all roads have some sort of water shedding slope the minimum slope in most conditions is 2%, usually each lane slopes in opposite directions, except in some steep terrain on narrow roads it is 2% for both lanes across the road, downslope
- Superelevation - this refers to the transition of the outer lane from sloping away from the corner to being banked with the corner - there is usually a 10-17m transition before the corner where this takes place - also, on some low speed limit roads there will be no superelevation except on the tightest corners.
- corner widening - this refers to the degree of extra width that is added to a road so certain types of vehicles can safely drive the road in their lane - common cutoffs are box truck/bus semi, and dual trailer semi.
most narrow mountain roads ban semi trucks, for this road I would guess only box trucks and buses are allowed ..
anyhow here are the diagrams:
corner widening: (any tips on euro standards would be welcome, I can only find us data)
http://onlinemanuals.txdot.gov/txdotmanuals/rdw/minimum_designs_truck_bus_turns.htm
superelevation:
http://techalive.mtu.edu/modules/module0003/Superelevation.htm
crosssection:
http://techalive.mtu.edu/modules/module0003/CrossSection.htm
( roadway, 2%typical, shoulder 4% typical, road edge 1:6-1:3) - I think the max roadway slope depends on local rainfall and drainage, I think 6% was the max I saw for paved roads - gravel has greater slopes for all but the road edge(grass/gravel embankment)
Edit: added some more from another post:
here, they did a pdf of all the road cross-sections here:
http://your.kingcounty.gov/kcdot/roa...000Roadway.pdf (.pdf 3mb)
from:
http://www.kingcounty.gov/transportation/kcdot/Roads/EngineeringServices/RoadStandards2007.aspx
this is from california and is in metric too:
http://www.myhamilton.ca/NR/rdonlyre...adDrawings.pdf (.pdf 9.6mb)
I can't find any specs from europe, don't know what to search for :tongue: and can't find anything about tarmac mountain roads .. but maybe it will help someone.
from:
http://www.fao.org/docrep/006/t0099e/T0099e03.htm#3.1 lots of info there. (these diagrams are for a 3m wide forest logging road -gravel- 2.4m wide trucks)