The height of a road safety barrier is an important feature to ensure that it contains and redirects a vehicle. The greatest concern is the barrier being too low as it increases the likelihood of a vehicle vaulting the barrier. Barrier systems have increased in height in recent years to reflect changes in the vehicle fleet, particularly an increase in the prevalence of vehicles with higher centres of gravity such as SUVs. Road resurfacing works can also result in a reduction in the effective height of a barrier.
Abraham blockouts can be retrofitted to some existing systems that are too low without having to replace the whole system.