Powered Rail

The Powered Rail is a block added in Beta 1.5. It was added to replace bug boosting, but as of Beta 1.5 boosters still work. It's operated by Redstone currents. In its unpowered state, it acts as brakes for any minecart which crosses its tile. In its powered state it will accelerate any cart to pass over it, up to the maximum speed of 8 m/s, at which point only a small amount of additional momentum can be added with powered rails.

Crafting
Powered Rails are made somewhat differently from normal rails; using gold instead of iron, and adding redstone to the bottom.

Powering
Powered rails act like redstone wire, and will pass the power to the next adjacent powered rail for nine blocks from the source. Powered rails have two possible states (similar to redstone wire):
 * Unpowered: Stops any minecart that passes over it. This is the default state.
 * Powered: Boosts any minecart that passes over it, subject to the rules below.

Powered rails (in the "On" state) will boost a minecart if any of the following is true:
 * 1) The minecart is already moving. The cart gets boosted in the direction the cart is traveling, making 2-way travel possible.
 * 2) The minecart is stationary, but one end of the powered rail is blocked by a block. The cart gets boosted in the only possible direction of travel (the direction that is not blocked). Used at the start of a minecart trip (launchpad), where the player can push a button to activate the powered rails to start the minecart moving from rest.
 * 3) The minecart is stationary, neither end is blocked, but the powered rail is on a slope. Gravity causes the cart to start moving downwards, which activates (1). Also used in the same manner as (2), but uses gravity to determine the direction boosted rather than a stop block.

Optimal use
A powered rail boost gives an occupied cart enough momentum to travel 64 tiles on a flat surface from a standstill, or eight tiles for an unoccupied cart. Having several powered rails next to each other will increase the cart's momentum further, but with diminishing returns after the first powered rail. Unlike the glitch boost system, booster rails won't provide the cart with much momentum past the cart speed limit of 8 m/s. A slower minecart gets a larger speed boost and vice versa, thus it is usually suboptimal to place powered rails next to each other, and instead better to space them out at regular intervals once the cart is initially traveling quickly. Glitch boosters remain useful as they produce higher momentum and require iron as opposed to gold.

The optimal spacing of powered rails is to use 1 every 26 blocks (that is, 1 powered rail followed by 25 normal rails, repeated) which maintains a constant minecart speed of 8m/s. Using 1 every 30 distance results in a negligible 2.6% speed decrease (an increase in travel time by factor of ~0.027 or a speed of 7.8 m/s) if gold is in short supply. Using 1 powered rail every 32 blocks results in a 10% drop in speed (an increase in travel time by a factor of 1/9 or a speed of 7.2m/s). Thus, the decision becomes how quickly one wishes to travel versus amount of resources used when deciding on the powered rails repeating interval (how far apart a single powered rail should be placed every n rails).

Four Powered Rails in a row is sufficient to boost a minecart from rest to the maximum travel speed of 8m/s, so a simple minecart launchpad is to attach a button to the start of the 4 consecutive Powered Rails with a stop block behind it.

Climbing slopes
Climbing slopes with powered rails can be inefficient. Placing a powered rail every other block is enough to climb up at a decent pace. Similarly, adding an additional booster for every block climbed over long tracks that go up and down can help preserve speed.

Additionally, a more effective but less practical way to use powered rails involves minecart boosters. The way to do it is to create a small track loop (4-6 pieces) next to your minecart track, and include 1-2 powered rails in the small loop. add a cart with weight in it (mob, chest, or furnace), and give it a little push, and it'll proceed to travel around the track at maximum speed. When riding a cart on your main track, when it passes by this loop, it'll immediately accelerate to or near max speed. The reason this is less practical is because it only works in one direction.

Use with Detector Rails
A Detector Rail will power the 4 blocks adjacent to it when a minecart (occupied or empty) is over it. It is thus possible to power Power Rails inline without the use of restone torches or wiring. This lends itself to one-way powered rail lines by placing a detector rail before the powered rail (with respect to the desired direction of travel). This way, occupied carts will only be boosted if they are traveling the "proper" direction; if carts are coming from the "wrong" way, they will be quickly brought to a stop by the unpowered power rail.

For a two-way powered rail line, there are a few options in increasing order of efficiency:
 * Place detector rails on both sides of the powered rail
 * Dig out two blocks beneath the location of the powered rail, place a redstone torch, then a block above it and the powered rail on top of the block
 * Place an activated Switch next to the powered rail

Placing alternate powered and detector rails up a 1/1 slope will not propel a cart of any kind more than 3 blocks upward due to a lack of speed, which is required to clear the booster before it returns to the "off" state. The cart will become stuck unless it is in a "train" of two or more carts, in which case the last cart in the train will become stuck. To go up a slope properly, the whole slope needs to be powered rails powered externally by redstone torches in order to maintain speed the same speed at the top as at the bottom.

Additional properties
Curved power rails currently only exist in the case of a T-junction. They do not currently function like regular rails in a curve (without being in a junction). It is possible to make a one-way curved railway using power rails, but not a bi-directional one.

When placing rails, regular rails prefer to curve towards the powered rail. In cases such as these, the south-west rule applies.

A cart traveling on a powered rail that collides with an object (wall, single block, player, other cart) will reverse direction. It will not reverse direction if it collides with a translucent block, such as Stone Slabs or Glass. If a track including powered rails is bordered by blocks acting as "buffers", the cart will indefinitely continue back and forth along the track. Having carts interact with each other on a short track designed this way can be used to chain multiple carts together as a "train". Once aligned, they will all move together at relatively the same speed.

How far the charge passes down adjacent rails is independent of the length of redstone wire. Even if the rails are connected to a redstone torch by 15 blocks of redstone dust, the rails will still be powered normally despite the fact that theyy should be out of range for the torch.

Stop Points
It is possible to make points in your track where a cart is stopped and then jumpstarted again by player input. This can be useful for creating checkpoints to certain sites of interest in your world. This can be done by using two powered track pieces on a one block incline, by having the first powered track piece going down, with the second powered track piece at the bottom and a button placed alongside the second powered track piece, so that the button is directly above the track. You can see an example of a stop point here.

When the cart comes to this point it will stop On the incline, allowing the cart to use gravity to start the boost when the button is pushed. Players can then either stay in the cart and carry on to the next stop, or leave the cart at the station for themselves/other players to use later.

Starting boost
Creating a simple initial boost device using 2 powered rails. Dig a hole 1 block deep and 2 blocks long. Place the powered rails inside the trench, connect one end to the track that you wish the mine cart to exit. Finally place the mine cart on the powered rail. Once power is applied to the rail the mine cart will be boosted out.

Bugs

 * If a Powered rail is only powered by another Powered rail diagonally up or down, you can destroy the rail powering it and it will continue to look and act like it has power until the block is updated. This can be used to have little to no power sources in your track design and up to 2/3 less powered tracks for uphill parts.
 * When you power a track, 8 tracks in both directions (excluding the track being powered) will be powered. If you have a 19 Powered tracks in a row [1,2,3...18,19] and you Power track 10, tracks 2-9 and 11-18 will receive power. If you add power to track 9, after powering track 9, track 1 will not be powered, even though it is within the 8 tracks. After this, if you remove power from track 10, power will be taken from track 9, however, the same tracks will be stay powered (tracks 1 which should be powered is not, and track 18 which is powered, should be unlit). If you power track 2, (or 18), you will get power in the next 8 blocks.
 * Doing this, you can power infinite tracks with only 3 torches. 1) If you power track 1, up to track 9 will be lit. 2) Power track track 9 (or last lit track) and 10 (the last unlit track). Putting power in track 9 will keep the previous tracks lit, and 10 will power the next. 3) Then unpower 1, it will still be lit, as 9 is lit, and in the 8 range. 4) Now unpower 9. 1 is still lit. Jump back to step 2.
 * This also means you can't power tracks in steps of 1 (unless you make something fancy with redstone circuitry). You would have to unpower everything, then power the one 8 steps away (you need n carts + 8 for the number of tracks)
 * There are currently no textures for curved power rails. However, they still work when placed at T-junctions powered by Redstone.

Trivia

 * Powered rails will always show as powered in the inventory even if destroyed and collected while it was unpowered.
 * Powered rails can curve, but they'll always be displayed as straight pieces.
 * With 1 powered rail, it provides enough momentum to travel from rest at a somewhat fast speed to a crawl for 65 meters (blocks).
 * When a powered rail with power has a powered rail added next to it, the second rail will not light, until the power is reset.