Car park safety is not a matter to be taken lightly.
After a number of high profile accidents in Australia where cars have driven over the edge of multi-storey car parks, there is a strong argument for the current Australian Standards for car park safety barriers to be increased in line with the UK.
One could be forgiven for thinking that steel safety barriers are sufficient to cope with an impact from slow speeds in car parks but the reality is that these types of accidents are likely to occur head on, with the resulting impact crushing the steel barriers and guard rails with devastating consequences. For instance, if we consider the repercussions of an accident involving a driver who has accidentally pressed the accelerator instead of the brake pedal, put the car into reverse instead of drive, or a parked car being pushed through a perimeter edge by a moving vehicle, there is a compelling argument for the need for stronger load bearing barriers, particularly in multi-storey car parks.
The existing Australian Standard AS/NZS1170.1 specifies that a car park vehicle barrier should withstand a 30-kilonewton measure of force which is equivalent to a 1,500 kilogram vehicle - a mid-size sedan – travelling at eight kilometres per hour. Yet when we consider actual car park vehicle speeds that often exceed the car park speed limits, and consider the weight of larger SUVs and utility vehicles which can be up to four times heavier than that average sedan, the existing load bearing specifications are insufficient to withstand an impact in today’s changing car park environment.
The UK is a world leader in car park safety, and while our standards bear many similarities to those in Britain, we have assumed different impact speeds that have not kept pace with changing vehicle trends. The British Standard BS6399 is renowned as being one of the most stringent car park safety standards in the world and was updated in 2002 to reflect the increasing use of heavier vehicles to ensure barriers could withstand a horizontal impact load of 150 kilonewtons for 1,500-kilogram for vehicles travelling at 4.5 metres per second or 20 kilometres per hour. This is a significant increase from the 30-kilonewton horizontal impact loads outlined in the AS/NZS1170.1.
The updates to the British standard also addressed the areas where there is a probability of increased speed risks and made recommendations in line with the impact force on barriers in those positions, for instance, opposite down ramps in multi-storey car parks or at the end of long aisles.
If we take a closer look at car park safety barriers, there are fundamentally two types – column mounted and floor mounted – and each is designed to stop vehicles from breaching the car park perimeter. These are then sub-divided into flexible or ridged options with flexible barriers designed to ‘give’ or deflect on impact which can absorb minor knocks without damage to the barrier or the impacting vehicle. Rigid systems will stop vehicles without deflecting, however, they may result in more damage to the barrier and impacting vehicle. Generally, a rigid system results in more damage to the barrier with repairs or replacement being less frequent but more expensive than a flexible system.
A column mounted system is a consideration for new build car parks as they have little or no footprint in the parking bay and thereby release more space for parking use. The barrier is mounted directly onto the structural columns with interim posts fitted if necessary. The car park design can take into account the weight of the system and the forces and stresses which are transferred from the barrier to the columns in the event of an impact. As there are no fixings to the deck itself, column mounted barriers can allow the use of thinner deck substrates and lighter deck materials.
Floor mounted systems, on the other hand, need to be fitted in an area away from the car park perimeter and are used where columns are not present. Floor mounted systems are also suitable for ramps, split levels, car park approaches or in front of doorways, walkways, plant and ductwork. They are the most common choice for perimeter refurbishments to minimise structural upgrading. Spring steel systems are the industry benchmark as they are flexible and designed to withstand high impact circumstances, buffering the impact rather than transmitting the force to mounting bolts.
As car park design trends continue to evolve without any change to the current Australian Standards, architects and designers should consider the safety needs in today’s car parks. While there is no legal requirement in place, choosing to install barrier systems that exceed current standards is a sensible consideration, particularly when designing multi-storey car park structures. Appropriate barrier systems that align with modern day vehicles will not only help reduce the risk of serious accidents, thus providing greater protection for drivers, passengers and pedestrians, but will also provide maximum protection for the actual car park structure.