Highway நடுவில் இவ்வளவு விஷச்செடிகளா?
6 Minutes
Why plants are grown on highway medians: learn how oleander prevents glare and saves money in this guide for students. A Tamil science lesson.
- How high beam headlight glare causes night accidents on highways
- Why walls, anti-glare screens, and big trees are not suitable
- Why oleander resists drought, repels cattle, and absorbs carbon
What this lesson teaches
Oleander plants are grown along highway medians primarily to block the blinding glare of high-beam headlights from oncoming vehicles and prevent nighttime accidents. Their controlled height, drought resistance, and natural toxicity make them a practical, cost-effective safety barrier compared to artificial structures or large trees.
The danger of headlight glare
When oncoming vehicles travel at high speeds at night with high-beam headlights switched on, the intense light temporarily blinds oncoming drivers. This sudden visual blinding is called glaring, and it causes drivers to close their eyes instinctively. On high-speed highways, losing vision even for a split second often leads to fatal collisions.
Why artificial barriers and trees fail
- Building concrete walls across more than 100,000 kilometres of highways is far too expensive for governments.
- Anti-glare plastic screens and mesh fences cut down glare, but installing and maintaining them nationwide carries a very high cost.
- Large trees grow wide, spread into driving lanes, block traffic, and increase the risk of serious crashes.
- Regular shrubs demand daily watering, which creates high recurring maintenance expenses.
Why oleander is the ideal median plant
Oleander, known scientifically as Nerium oleander (arali), naturally grows only up to 20 to 25 feet tall, which means it blocks headlights without encroaching into traffic lanes. It is a drought-resistant shrub that survives primarily on rainwater, removing the need for expensive daily watering routines. Because oleander is a poisonous plant, grazing animals like goats and cattle avoid eating it, which stops livestock from wandering onto high-speed lanes and causing collisions.
Pollution control and appearance
Oleander shrubs absorb harmful exhaust gases emitted by passing motor vehicles through a process called carbon sequestration. This natural carbon absorption significantly lowers roadside air pollution. In addition, its bright pink, white, and yellow blooms beautify roadways and can be harvested and sold in flower markets. While flowering shrubs such as bougainvillea are also planted on medians, oleander remains the most economical and resilient choice.