查了一下 wiki，才發現 WRC 本身是設計成跑不同的路面，
而不是我本來想的特地選路況差的路面。

The series currently consists of 13 three-day events driven on surfaces ranging from gravel and tarmac to snow and ice.

不同場地有不同的路面設計，wiki 上列了下面幾種。

http://bit.ly/SsosEx

Tarmac (柏油)
Gravel (碎石)
Mud 泥巴
Tarmac with Mud
Ice/Snow covered Gravel
Tarmac with Ice/Snow