Why textures transparent?

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Hi! Good day.I am planning to do a new kind of road(see the screenshot). It has trees on both sides of the road. But it seems not very well...because those tree's textures is transparent. It look not real.

Can anyone help me solve this problem? Thanks.

[Slavatrainz 1 721]

You can use the trees made ​​by the developers. But I think it is better not to put trees. Let the player decides where to put them.

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My other works are also