I understand that it’s not the most hospitable environment for most plants (salt, car accidents, minimal animal traffic) but that space gets mowed to keep what grows there short. Why not have some wildflowers, native grass, or even trees there? Trees would act as an extra barrier between such fast traffic
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Mainly, budgets.
Usually the state’s department of transportation is in charge of maintaining these areas and the simplest and cheapest option is use a tractor mower to keep it in check. This gives them easy access to the cable barriers that prevent crossover accidents. And that’s the limit of maintenance – just let whatever grows grow and keep it somewhat maintained by mowing it periodically.
Now, trees, would seem like a good option. Trees have branches that need to be pruned otherwise they fall into the road if they’re close enough. Wind storms and severe weather can also knock trees over into the road. Car accidents (especially semi accidents) can also knock a tree down into the other side of the highway.
Now, yes, the trees can be maintained to prevent a lot of this. However that would require every tree to get individual attention. DOTs just generally don’t have that kind of budget. So, cable barriers and tractor mowers it is
Most places have regulations about how far away trees must be from roads with high speed traffic so people don’t crash into them. You also don’t want to attract wild animals like deer close to the highway.
Vegetation is harmed by the salt used on highways where there is snow/freezing. Between airborn spray and grown absorption from salty runoff, trees and such wouldn’t do well.
It’s also a safety feature, where oncoming traffic might see an accident, highway patrol can patrol twice as much traffic by seeing both sides and being able to U-turn.
But there are some places where I have seen vegetation between highway directions (in Georgia, Florida).
I remember median strip bushes [like these](https://1.bp.blogspot.com/-gy5oP1nEaeU/XToB4trzhZI/AAAAAAAAi3o/HMEU9-pD9HgPR8vPxUugNj6_WB8DfTWWgCLcBGAs/s320/IMG_3507.JPG) everywhere in California growing up. Not sure how popular they are now, though.
Trees are, generally speaking, hard immovable objects and ramming into one at high speeds can easily be fatal. They’re pretty poor barriers. Sure, they’ll block you from crossing the median but at what cost? Guardrails and cable systems they have in the medians are designed to deflect fast moving cars back onto the road or slow them down without outright stopping them. Even many newer street signs and light poles are generally designed to break away when hit. Trees can’t be designed the same way and abrupt stops are not good for your health.
Native grasses/wildflowers might seem like a good compromise, but it’s practically impossible to have JUST native grasses/wildflowers and keep out brush and trees.
In Texas, TxDoT actually does actively sow native wildflowers (like the iconic bluebonnet) and some grasses in areas that don’t have groundcover yet and doesn’t mow in spring while the flowers are in bloom.
The couple of months not mowing saves money, and since they don’t mow until after the flowers have finished producing seeds, they’ll self-seed the next year, so it’s very cost efficient, and since the areas still get mowed in summer/fall/winter, brush and trees never have a chance to get established.
Those medians are often clear zones, so if you get run off road you don’t cross into the other direction of traffic. Imagine you were going 60mph and you slammed into a mature established tree, you would probably be dead.
The purpose of the median is safety. They are generally intended to do one of two things. A. Prevent a vehicle that leaves the roadway from crossing the median for a head on collision. B. To protect the occupent as much as possible during the incident. Hitting a tree or other large piece of vegetation can kill the occupant and knock the tree over to do other damage. All current medians and guard rails are there to absorb energy and prevent a vehicle from crossing. Large barren areas that are graded correctly can also achieve the same thing.
In California, most medians are planted except for desert areas. Have you ever seen the blue bells in Texas planted all over the roadsides, underpasses,, and medians. Thanks Ladybird.
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