Just a small suggestion, that perhaps should've gone in the topic by that name...
The Basics:
Basically just a Track block that can be placed without a block under it, but has to have a normal, Detector, or Booster Track on at least one side of it (to prevent huge cheap bridges made of these).
Properties:
Bridge Tracks will flip up like Trapdoors when either right-clicked or powered with a Redstone signal. When up, they will allow carts that hit them from the "back" end to drop "through" them and simply stop carts that hit them from the "front" (hinge) end. They also have a collision box the width and length of a block but a thickness of near-zero, so that they basically have a flat collision box just like you would if you had another block under a normal Track. When down, they will act the exact same way as normal Track except for the fact that they have a collision box and (obviously) don't need a block under them.
Appearance:
They will look like normal Track with a 3D wooden box under them somewhat like a wooden Pressure Plate. They can also be activated by adjacent Detector Rails.
Edit: Changed the physics portion and organized the ugly wall of text. It still is a bit confusing, though...
The Basics:
Basically just a Track block that can be placed without a block under it, but has to have a normal, Detector, or Booster Track on at least one side of it (to prevent huge cheap bridges made of these).
Properties:
Bridge Tracks will flip up like Trapdoors when either right-clicked or powered with a Redstone signal. When up, they will allow carts that hit them from the "back" end to drop "through" them and simply stop carts that hit them from the "front" (hinge) end. They also have a collision box the width and length of a block but a thickness of near-zero, so that they basically have a flat collision box just like you would if you had another block under a normal Track. When down, they will act the exact same way as normal Track except for the fact that they have a collision box and (obviously) don't need a block under them.
Appearance:
They will look like normal Track with a 3D wooden box under them somewhat like a wooden Pressure Plate. They can also be activated by adjacent Detector Rails.
Edit: Changed the physics portion and organized the ugly wall of text. It still is a bit confusing, though...
Decent idea non the less.