New rail block for setting minecart speed

My idea to solving the problem with minecarts being slow is to give all minecarts a variable that indicates their current maximum allowed speed.
This stat can be changed with a new rail type based on the redstone signal strength it currently receives.
- No redstone power would likely set minecart speed to the current default.
- When given a weak redstone signal it would set the max speed to something lower than default.
- When given a strong signal it would set the max speed to something higher than default.

I think this system would make it so no damage will be done to current minecart systems while also making it easy (from a gameplay perspective) to upgrade existing rail lines to higher speeds.

The new rail itself does not accelerate minecarts.