Road Items

Road Items refers to any item that can be placed directly on the path of the Bloons, excluding Bloonberry Bushes (BTD5-exclusive), Monkey Boosts and Red Hot Spikes (BMC-exclusive). They include Road Spikes, Exploding Pineapples and Monkey Glue.

Road Spikes
Road Spikes is a road item that made its debut in Bloons Tower Defense 2 and have been in every subsequent Bloons TD game since. Road Spikes are a group of spikes which pop up to 10 (11 in BTD 5) bloons upon impact. Road Spikes only last until the end of the round. In Bloons TD 3 there is a number indicating how many spikes are left, with each spike popping 1 bloon, while in later games, it degrades. Road Spikes will disappear at the end of the round if not completely used up. Road Spikes cost 25 on Easy Difficulty, and 30 on Medium and Hard. The prices are the same for every game that Road Spikes are in. In Apopalypse Mode, Road Spikes and Monkey Glue last for an indefinite time since there are no round endings. Road Spikes are best used for popping Bloons that escape your defenses because they don't earn enough money to pay back their purchase.

Pineapples
Debuted in Bloons Tower Defense 3, the Pineapple is a placeable road item in the Bloons Tower Defense games. Even though it doesn't explode until 3 seconds after being placed (aside for the Grilled Pineapples Premium Upgrade in BTD5 and BTD5M), it is still regarded as a good defense for M.O.A.B.'s on BTD3. On Easy Difficulty the Pineapple costs 20 money, and on Medium and Hard it costs 25 money. It pops 2-4 layers of bloons except in Bloons Tower Defense 4 and 5, where it only pops 1 layer.

Monkey Glue
Monkey Glue is a roadblock that debuted in Bloons Tower Defense 2. Each Monkey Glue is enough to slow down 20 Bloons before wearing out. Monkey Glue only lasts until the end of each round. In Bloons Tower Defense 2 & 3, Monkey Glue costs 40 coins. In BTD app (For iPhone/iPad), Monkey Glue costs 35 coins. In Bloons Tower Defense 4, Monkey Glue is reduced to 10 coins. In Apopalypse Mode, Monkey Glue, as well as Road Spikes, lasts for an indefinite amount of time since there are no round endings. Ceramic Bloons and MOAB-Class Bloons are immune to Monkey Glue, as well as the Glue Gunner tower (which probably shoots Monkey Glue) without the Corrosive Glue upgrade. Monkey Glue is best used for the early rounds.

Trivia

 * Bloons TD Battles does not have the standard Road Items; however, they do have White Hot Spikes, which cost 1 each.