The Trio Elétrico is a big truck, driven very slowly, loaded with thousands of watts of sound equipments and with a band playing on the top. Surrounding the truck, there is a big rope carried by hundreds of security guards. This structure is organized by a private company and is called bloco. Each bloco sells a different T-shirt called abadá. This T-shirt is your entrance ticket and allows you to get inside the rope area. The biggest blocos can have over four thousand people, dancing, drinking, kissing and having fun. The people who aren’t in blocos, and therefore are outside of the rope areas around the trios, are called pipoca. The name comes from people jumping up and down like popcorn popping to the music rhythm. Inside the rope, security is good and the situation is reasonably organized.
A good option is to buy an abadá for a camarote (a stand with a balcony that line the parade route) from which you can watch the trios. The most famous blocos, but not necesarily the best, are Timbalada, Crocodilo led by Daniela Mercury and the traditional afro group Olodum.
Barra parade starts at the Farol da Barra (the light tower) and procedes along the ocean until Ondina. The course takes about three hours. Nowadays there is a tendency for the bigger names to play on this parade.

Avenida parade starts at Campo Grande, by the Avenida Sete de Setembro to Praça Castro Alves.
The Salvador Carnival is heavily policed, specially in Barra. Stands with five or six seated police officers are everywhere and the streets are constantly patrolled by police groups moving in single file usually arriving quickly to break up into any incident. Remember you are in a poor city with plenty of inhabitants who would happily try to buy their food and drink by pickpocketing in an often unsubtle manner, i.e. hands in your pockets. How to avoid this? One way is to stay out of and away from the pipoca (the Carnival open crowds)
There is plenty of beer, stockpiled along the streets, stacks 2 meters high, everywhere. Be careful when moving around, do not wear any jewellery or wristwatches and only carry a minimum amount money. Salvador can be a dangerous place if you are on your own.