Austroads has released a report which identifies factors that contribute to the occurrence and severity of crashes adjacent to and within tunnels and suggests remedial treatments.
A preliminary examination of recorded road crashes immediately adjacent to and within a selected sample of Australian tunnels found that, while tunnels are relatively safe when compared with other parts of the road network, crashes in or near them are a significant source of road trauma and cause substantial delays to road users across the road network.
As road tunnels form an important part of the road network, there is a need to ensure motorists can travel in a ‘Safe System’ consistent with the National Road Safety Strategy 2011–2020. Such a system acknowledges that road users will inevitably make mistakes, and that when they do, they should not be penalised with death or serious injury.
The main findings of the study were:
- driver behaviour is a major factor in the occurrence of crashes
- most crashes involve vehicles travelling in the same direction (i.e. rear-end, side-swipe and lane changing); this is as a result of variations in driver speeds, unsafe vehicle headways (i.e. vehicles travelling too close to each other or inadequate travel time gaps between vehicles), poor lane discipline, unsafe passing and high speeds for the conditions
- changes in driving conditions pose the greatest crash risks
- variations in light levels when entering tunnels and the ‘quality’ of lighting within tunnels are crash risk factors
- trucks travelling through tunnels increase crash risk and the risk of high-severity crash outcome
- the absence of a shoulder or narrow shoulders and narrow lanes increases crash risk
- merge and diverge areas in tunnels increase crash risk as there is an increase in vehicle manoeuvring.
The report recommends:
- reviewing the type and placement of signage to reduce information overload and simplify the driving task
- review and regulation of lighting levels at tunnel entries and through the transition zone, to minimise lightings variations over a short distance
- using variable message signs to advise users of incidents and driving requirements, particularly in long tunnels
- reviewing truck access to tunnels and considering restrictions to the lanes they are permitted to travel in
- installing speed cameras in all road tunnels
- using signage to discourage overtaking and encouraging tunnel users to maintain a safe distance between themselves and the vehicle ahead
- providing shoulders or breakdown bays, and in their absence ensuring safety management systems are provided to reduce crash risks
- investigating the application of low-cost perceptual countermeasures treatments to improve safe driver speed behaviour, lane discipline and safe driver headways
- reviewing the Austroads Guide to Road Tunnels to ensure it reflects best practice in new tunnel construction and retrofitting older tunnels.