Answer: Tulip trees are huge -- Liriodendron tulipfera can grow easily to about 80 feet tall and maybe 50 feet wide in the landscape, larger in the wild. So depending how you planted in relation to the driveway it could cause some problems as the trunk expands and the root flare widens in addition to the sheer size of the root system. Unless your drive is very long and the setting is park-like, it may not be that suitable.
Ornamental pears are much smaller trees but are known for their surface rooting over time as they age. Again it would depend on how you sited it in regard to the drive. This tree usually grows about 15 feet wide so you could plant it about ten feet from the drive and avoid too much trouble.
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