Rear overhang

What is the rear overhang?

A vehicle’s rear overhang is the distance between the vehicle’s rear and its rear overhang line.

Where is my rear overhang line?

If a vehicle’s rear axle group has only 1 axle, the rear overhang line is the centreline of that axle.
If a vehicle’s rear axle group has 2 axles and 1 has twice the number of tyres as the other, the rear overhang line is one-third of the distance between the 2 axles and closer to the axle with most tyres.
If a vehicle’s rear axle group has a steerable axle, you can’t count that axle unless:
1. the group has only 1 axle, which is a steerable axle; or
2. all the axles in the group are steerable axles.
For other axle groups – for example, when all axles are fitted with the same number of tyres – the rear overhang line is the centreline of the axle group.

Rear overhang limits

The pictures in this section are just examples. As discussed above, vehicles have different axle and tyre configurations, which determine the location of the rear overhang line.

Rear overhang on rigid trucks – Lesser of 3.7m or 60% of wheelbase

3 axle controlled rigid truck - rear overhang lesser of 3.7m or 60% of wheelbase

Rear overhang on semitrailers and dog trailers – Lesser of 3.7m or 60% of ‘S’ dimension

3 axle semi trailer - rear overhang lesser of 3.7m or 60% of 's' dimension

The ‘S’ dimension is the distance between the trailer's front articulation point and its rear overhang line

Rear overhang on a pig trailer – The rear overhang on a pig trailer must not exceed, the lesser of the length of the load-carrying area forward of the rear overhang line and 3.7m

3 axle pig trailer - rear overhang line 3.7m

Rear overhang on other vehicles, such as a bus – Lesser of 3.7m or 60% of the wheelbase

3 axle controlled access bus - rear overhang lesser of 3.7m or 60% of the wheelbase

For vehicles fitted with retractable axles, rear overhang requirements must be met in retracted and unretracted positions.

Measuring your rear overhang

The following pictures show where you should measure your rear overhang, based on different axle groups and number of tyres. They are just examples, and other variations may apply.

Example	Axle type	Rear overhang
4-axle low loader	Last axle is steerable	Centre of second axle to rear of table
6-axle platform trailer	All steerable	Centre of axle group
3-axle controlled access bus	Last axle is steerable	Centre of first axle in rear axle group
3-axle controlled access bus	Rear axle group where the first axle has 4 tyres and second axle has 2 tyres.	1/3 of axle spacing closer to the axle with 4 tyres
3-axle truck and 4-axle dog trailer	Rear axle group fitted with dual tyres on each axle	Centre of last axle group

Rear overhang exemptions

Some notices and permits exempt a vehicle from the length requirement for rear overhang in the MDL Regulation. If you are operating under one of the follow notices, there may be additional rear overhang allowances available.

Notices can be viewed and downloaded from the NHVR national notices page.