Given the prevalence of hoon-like behaviour on the streets of many parts of Australia, it's important for property owners to ensure the safety and security of their built assets should wilfully reckless driving result in a vehicle collision.

The danger of reckless driving is tragically exemplified by the recent death of 17-month old infant Tatiana Tauaifaga in the Sydney suburb of Constitution Hill, as a result of a vehicle collision during the police pursuit of 22-year-old car thief Christopher Chandler.

In turns out that one of the most effective means of protecting buildings and property assets from careening automobiles is actually one of the simplest and least obtrusive, with civil engineers from Penn State University discovering that calculated boulder placement can serve as a highly effective barrier against potential vehicle impacts.

The team of researchers led by Tong Qiu, assistant professor of civil engineering at Penn State, had been asked the US Department of State to determine if a boulder would be an effective means of preventing a truck from ramming into one its buildings either at home or overseas.

Boulders were chosen because they are a simple, low-tech solution that can be employed in a multitude of scenarios.

“You can design all kinds of systems, but then the system has to be deployable overseas,” said Qiu.

The team devised a simple model for selecting a boulder with just the right dimensions for stopping a large vehicle in its tracks, taking into account the various physical properties of the soil and the speed of the truck in addition to the boulder itself.

“We provided a tool of the Department of State to be able to size a boulder for embassy protection,” said Qiu. “It’s a quick assessment tool so they can do it very quickly.”

Full-scale field tests at Penn State’s Larson Transportation Institute concluded that boulders of an appropriate size can indeed serve as effective means for blocking incoming vehicles, with the key factors being the placement of the boulder at an appropriate depth and the prevention of rotation of the boulder as a result of vehicle impact.

The conclusions reached and tools developed by the Penn State researchers should have beneficial implications for property owners in Australia, providing them with the reassuring knowledge that a rock barrier of an appropriate size will be capable of stopping an unwanted vehicle collision.

In many circumstances boulders are preferable to conventional methods for preventing vehicle access such as bollards.

Rocks and boulders can be integrated seamlessly into the swards or nature strips of many larger properties, perhaps even enhancing their overall aesthetic effect. The use of bollards in such circumstances can look incongruous, however, and compromise the desired natural appearance.

Boulders can also serve as a more economical option depending upon the size and type selected, with Australian landscape companies typically providing quotes of several hundred dollars for the procurement and transportation of large granite rocks. Cheaper rates are also available should rocks be conveniently obtained during excavation operations.

This compares favourably to the price of bollards, each of which can cost a similar amount at the higher end of the market, and a greater number of which may be required to afford commensurate levels of protection to a property from vehicle collisions given their much smaller dimensions.