4.5.2 Vertical Curves
Normal stopping sight distance requirements will apply for all vertical curves, crests and sags. Since tunnels will be artificially lit, the sight distance criteria normally applied to sag vertical curves will not apply. Desirable comfort criteria will apply provided drainage and sight distance requirements can be accommodated.
Sag vertical curves must be designed so that overhead obstructions (e.g. lighting, signs, opacity meters, ventilation fans) will not interfere with the line of sight. In analysing the requirements for sag curves and the impact of the roof height available (including the effect of equipment suspended from the roof), the eye height to be adopted is 2.4 m (truck driver eye height) with an object height of 0.8 m (car tail light).