A head on crash is very severe when compared to other types of highway crashes. It takes just a few seconds for vehicles moving at highway speed to cross the median and collide with the vehicles from the other side of the lane. Median barriers are effective in separating the opposing traffic streams of a road physically. It also helps to stop vehicles moving into the opposite lane accidentally and to avoid pedestrians crossing the road at risky places. In 2006 there were 821 median cross over accidents that resulted in fatalities on U.S National highway system alone.
The factors that influence the selection of a barrier system are the type of the vehicles involved, roadway geometry and the potential severity of any head on crash incident. In most locations a standard barrier capable of redirecting the vehicles to the right area would suffice. However, in locations with complex geometry, adverse environmental conditions, heavy truck traffic and high traffic volumes and speeds, a barrier with high performance is necessary.
There are basically three categories of median barriers. They are detailed below,
The most common type of the median barrier in use today is the concrete barriers.
– They are widely used because of their maintenance free characteristics, low life cycle cost and safety performance.
– They are very effective in avoiding vehicle crossover collision on accident prone regions with high traffic volumes and speed.
– They can also be used in areas where the required median widths to install other types of barriers is not available.
– Jersey barrier is a modular concrete barrier that allows the vehicles to collide on its lower slopped face, pivoting it back in its original direction.
– Comparatively the installation cost of rigid barriers is high.
Semi rigid barriers
It is otherwise called as guardrail or guiderail. These rails are made of metals and they are collected in segments supported by posts or blocks.
– Unlike rigid barriers, semi rigid barriers are designed to absorb more energy from the impact and the entire assembly move or deflect during the crash. Hence, lesser damage to the vehicle.
– Installation cost is less.
– They are only suitable in the areas that are not sloppy and have good soil condition.
– The cost of the repair following an impact is high.
Typically it consists of multiple cables that are connected to each other in a series of posts.
– It is the most versatile and forgiving barrier system in minimizing the median crossover crashes. This absorbs most of the energy of the impact and reduces the forces exerted on the vehicles and its occupants.
– Considerable time and cost must be spent maintaining, endangering motorists and workers during each repair.
The other factors that are considered before deciding the barrier type are road alignment, crash history and the number of lanes.