Road Spikes (pre-BTD6)

"Place these on the track to pop bloons. Each pack of spikes can pop 11 bloons before being used up. Use these to get bloons that escape past your towers."

- Bloons TD 5 Description

Road Spikes are road items that made their debut in Bloons Tower Defense 2 and have been in every subsequent Bloons TD game (except Bloons TD Battles Flash) before the Bloons TD 6 Generation, which removed them. Road Spikes are a group of spikes which pop up to 10 bloons upon impact in most games. In Bloons TD 5 Flash, they instead pop 11 bloons. Tack Awesomizer can boost this to 22 bloons.

Road Spikes cannot pop Lead Bloons and Frozen Bloons, because they are sharp. However, placing Road Spikes in the radius of a Monkey Intelligence Bureau will only pop the Lead Bloon layer and not harm their children.

Road Spikes only last until the end of the round. Road Spikes will disappear at the end of the round if not completely used up. In Apopalypse Mode, Road Spikes and Monkey Glue last for an indefinite time since there are no round endings.

Road Spikes cost 25 on Easy Difficulty, and 30 on Medium and Hard in every game that Road Spikes are in.

Starting from Bloons Monkey City, there are also Red Hot Spikes that have normal-type damage that can be either bought for premium currency or earned for free as rewards.

Appearance
Road Spikes have undergone many minor appearance and animation changes across the games they appear in.

In Bloons TD 2, Road Spikes have different sprites for its icon: before placing down and after.

In Bloons TD 3 there is a number indicating how many spikes are left, with each spike popping 1 bloon, while in later games, the pile degrades with each pop removing an individual spike.

In Bloons TD 4, Road Spikes always show on the track in the same orientation, but in Bloons TD 5, they rotate before being placed again, and after being placed once, they are return to the former position.

In Bloons Monkey City, Road Spikes have different artwork in the 'My Monkeys' tab then the art shown in Bloons Tower Defense 5 when they are first unlocked.

Strategies
In general, Road Spikes are best used for popping Bloons that escape your defenses because they don't earn enough money to pay back their purchase.

In some cases, if the Road Spikes are not spread out, it can cause a bloon's descendants to spawn in front of the spikes, causing them to not be popped. Therefore, clicking on a Yellow Bloon with a pile of spikes might cause a Green Bloon to leak.

Bugs
With glitches that allow the player to place towers anywhere, it is possible to place Road Spikes off the track.

In Bloons TD 4, there is a glitch where fast Bloons can travel a short distance over road spikes before popping, causing the bloons that spawn from them to miss the Road Spikes completely.

In Bloons TD 5's Co-Op Mode, you can place Road Spikes, but they often take too much time to load, and when they loaded, they would have already leaked. In BTD5, the left player sees the bloons correctly, the right player sees bloons with time delay, so only the left player should use Road Spikes.

Quotes
"Road Spikes can be used in a panic to get those last few bloons, especially those nasty camo bloons. Very useful for winning with no lives lost. You get 5 stacks of 10 spikes each for each Spike Shack built."

- BMC Flash description

Trivia

 * Tack Awesomizer combined with Double Cash can return the cost used to buy the Road Spikes. (Flash only)
 * This will make Road Spikes get $44, while they cost $30, giving you a free $14 cash if you popped all the bloons.
 * In Bloons TD 5, if you have an activated Spikes R Us Speciality Building with the third upgrade, you get 1 free set of road spikes every round.