Mainly from a discussion on the tram track and the transverse profiles filled with ridges and slots.
Here's a way to take a profile of a defect in the road surface, with a profile comb.
Here's a profile comb
http://www.screwfix.com/p/forge-steel-profile-gauge-10/7233c
Put the comb down on the profile and push down the elements so that the lower ends take the shape of the rail-road profile.
Take a sheet of card and place it against the comb so that with a pencil or pen you can trace the transferred profile from the upper ends on to a flat surface for measuring up later.
You can also get a more subjective assessment using a straightedge (joiner's folding ruler)
https://www.flickr.com/photos/h52/21748824728/in/dateposted-public
Using coins of the realm you can measure the gaps - a £2 coin - 2.5mm - 3mm = limit for height of manhole frames & other ironwork above new road surface. Tactile tramlines = 5mm = 2 coins