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How are speed limits set in NSW?

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Why can you drive faster on some roads than others? Who is responsible for setting the speed limits on our roads and can the speed limits be changed?

NRMA’s Motoring Advice team get asked many of questions, so we got to the bottom of how speed limits are set in New South Wales (NSW).

Why do we have speed limits?

The setting of safe speed limits is an integral part of protecting road users' safety on NSW roads. According to Transport for NSW, almost 40% of all road related fatal crashes and 16% of injury crashes in NSW have speed as a factor.

Who sets the speed limits in NSW?

The Road Transport (Safety and Traffic Management) Act 1999 empowers the Roads and Traffic Authority (RTA) (now, Transport for NSW) ) to set the speed limits on NSW roads through traffic regulations. Transport for NSW determines the speed limits for all roads and road users based on a standardised set of guidelines and national agreements which aim to regulate the maximum speed of travel under good road and travel conditions.

What are the standardised guidelines?

Speed limits are set in accordance with the NSW Speed Zoning Guidelines. These guidelines are developed and applied by road safety experts and traffic engineers from Transport for NSW. The guidelines themselves, are based on international and evidence-based best practice in speed management, Australian Standards, Austroads Guides, state legislation, government policies and plans. They’re kept up-to-date through incorporating the latest advances in research and technology, as well as integrating road safety objectives and traffic management initiatives.

How are speed limits set?

The key principle in setting speed limits for a length of road is that the established speed limit should reflect the road safety risk to road users, while maintaining the ability of people to easily get to their destination. A number of key factors are considered in establishing the speed limit including; crash profile, width of lanes, road function, road use, roadside development, road characteristics, road alignment/profile, traffic mix, crash history and the presence of vulnerable road users, such as pedestrians, motorcyclists and bicycle riders.

Other factors include the number, type and frequency of driveways and intersections (traffic lights/roundabouts etc) which indicate potential conflict points. These conflict points are considered because they allow vehicles to turn across traffic where there is a chance of a ‘t-bone’ type of crash occurring.

Are speed limits set in stone?

While speed limits have evolved over time, they have also been increased and decreased in consideration of the road safety impact and its changes. For example, in 1979 the open road limit was increased from 80km/h to 100km/h. While in 2003, the default urban speed limit was decreased from 60 km/h to 50 km/h resulting in a 20 per cent reduction in pedestrian injuries.

New regulation such as school zones have seen speed limits reduced to 40km/h during teaching periods. The area around the Manly Esplanade has commenced a trial with a speed limit of 30km/h in July 2020.

Why do speed limits seem lower than they could be?

Circumstances such as crash history – which greatly influences the setting of a speed limit for a length of road might not be apparent to road users. It’s also important to remember that there is a level of risk associated with the speed limit relative to that road. Because of this, Transport for NSW has made extensive efforts to ensure that speed zoning is consistent throughout the state and accurately reflects the safety risk on a given length of road.

Can the speed limit of a particular length of road be changed?

The NSW road network is a dynamic system. The key guidelines considered in the establishment of a speed zone may change over a period of time, so it’s important for speed limits to be reviewed to ensure the adopted speed limits for a road reflect the current risk to road users. While Transport for NSW has teams who constantly monitor and review the lengths of NSW road networks for correct speed limits, they have also made it easier for the community to take an active role in providing their feedback by creating the Safer Roads website.

What difference do small changes to speed limits make?

The ‘kinetic energy’ (energy associated with the movement of an object) that a vehicle has does not increase linearly with its speed. Energy increases with the square of an objects speed. So a vehicle travelling twice the speed has four times the energy.

Lower urban speed limits (30km/h or 20 miles per hour) are increasingly becoming the norm around the world. In the Sydney CBD, around 90% to 95% of trips are by pedestrians or cyclists. In the event of a collision between a vehicle and a pedestrian/cyclist, small changes to impact speeds significantly change survivability.

  • Impact speed of 30km/h, around 5-10% of people will die
  • Impact speed of 40km/h, around 25-40% of people will die
  • Impact speed of 50km/h, around 70-80% of people will die
  • Impact speed of 60km/h, around 100% of people will die

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    Extensive research by Transport for NSW, has shown that even slight reductions in travel speed can result in substantial reductions in the occurrence and severity of road crashes. There was a 26 per cent reduction in casualty crashes on the Great Western Highway when speed limits were reduced from 110 km/h to 100 km/h in 2000. Similar reductions in speed limits on Victorian freeways led to an estimated 19 per cent reduction in the casualty rate.

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