Department of State GrowthTransport

2 Plus 1 Road Design

The 2 Plus 1 Road Design forms an important part of the Department of State Growth's "Safe System' approach to road safety.

The 2 Plus 1 design incorporates two lanes in one direction and one lane in the opposite direction; separated by a flexible safety barrier.

2 Plus 1 Road Design

The configuration is alternated approximately every 1.5 kilometres, depending on road alignment.  This allows drivers travelling in each direction to have safe and regular overtaking opportunities.

The benefits of a 2 plus 1 road design

The 2 plus 1 road design significantly reduces the risk of head-on crashes and provides additional safe overtaking opportunities for motorists on Tasmania's higher speed roads.

Tasmania has a history of head-on and run-off-road crashes. Veering out of the vehicle lane can result in fatalities or serious injuries. In rural environments, head-on crashes are the most severe type of crash. Head-on crashes occur when vehicles stray into opposing traffic lanes because of: driver inattention or impairment; over-correcting after straying into the road shoulder; excessive speed; and inappropriate overtaking. The Department of State Growth has identified locations where there is a high level of head-on crashes on Tasmania's higher speed road network. At these sites adding a third lane and applying the 2 plus 1 road design with a flexible median safety barrier, significantly reduces the risk of head-on crashes and provides safe overtaking opportunities.

Choosing a 2 plus 1 road design over constructing a dual divided carriageway

The addition of a third lane and implementing the 2 plus 1 road design with a flexible median safety barrier improves traffic flow by providing overtaking opportunities approximately every 1.5km.

Although dual divided carriageways provide superior overtaking opportunities, the traffic volumes on the majority of Tasmania's higher speed road network are too low to justify building them.

The cost saving from not constructing a dual divided highway means more of Tasmania's road network can be treated with road safety initiatives.

Flexible Safety Barriers - The 'Safe System' approach