Why Spain plants oleander trees in the middle of motorways

These colourful bushes line high capacity roads all over southern Spain

Spain is one of the safest countries in Europe to drive in, ranked tenth by the European Transport Safety Council. The traffic authorities are continuously making improvements to reduce risk, and today most of the nation’s motorways and dual carriageways boast lots of safety measures, like several lanes, wide shoulders and plenty of exits and entrance ramps.

But there is one unusual element that’s used all over southern Spain to protect drivers that goes largely unnoticed: oleander trees.

These colourful bushes, usually adorned with beautiful white or pink flowers, can be seen planted close together for miles and miles along the central median strips of high-capacity roads, but they are far more than decoration.

Oleanders are tough customers and grow dense foliage and branches, so they create an ideal barrier to prevent cars from accidentally crossing over into the opposite lane. They also tend to be very tall, so their leaves and flowers will minimise the dazzle from headlights at night. To a lesser extent, these trees can also help dull traffic noise.

However, oleanders can’t just be left to their own devices. These hardy trees can easily reach three metres in height and if they’re not pruned regularly, they can cause a dangerous tunnel effect. As explained by the General Directorate of Traffic (DGT), the tunnel effect occurs as a result of what’s known as ‘perceptual cataclysm’. That is, as the speed of traffic increases, the angle of vision when perceiving objects (other cars) and people on the road is reduced.

Image: Centro Medico Gran Via