Police Roadblocks are set up on the road in an attempt to block the player in pursuit. They appear at a 3 Star Wanted Level. The Police Roadblocks first appeared in Grand Theft Auto 2 and have featured in every Grand Theft Auto game since.
GTA 1 introduced with only police cars blocking the roads, and the same goes with GTA London '69 and GTA London '61, in GTA 2 it is easier for the player to escape as there are laced gaps between neighboring vehicles, secured only by easy-to-be-rammed-through barriers, that even leave the player's car nearly undamaged. GTA 2 also introduced higher level police, FBI and military road blocks.
Roadblocks are featured in all of the games in the 3D Universe. In GTA Vice City, GTA Liberty City Stories and GTA Vice City Stories, the Police will set up stingers and driving over them will result in bursting the players tires and the player will be unable to drive the car properly. In GTA San Andreas, in the initial cutscene of Puncture Wounds there is a reference to the police using stingers, but they never actually set them up as a part of a roadblock.
Depending of the wanted level, some variations will occur during the pursuit. For a 2 stars level, police cars are placed on the road and some police officers will be waiting to shoot the player. For a 3 stars level, there would be officers deploying spike strips in order to pop the vehicle's tires. For a 4 stars level, transport vans are used, which would be heavy for some basic cars. For a 5 stars level, undercover SUVs are used, which are lighter than the vans, but are still heavy for basic cars. Finally, for a 6 star level, military transport trucks are used, being even heavier for most vehicle's classes.
The changes from the previous games to GTA IV are much of the same but the Police will set up roadblocks on main bridges (those that connects the main islands) and the Booth Tunnel, on each entrance. On a locked island, they will put concrete block and a vehicle on each side preventing the player to pass through the bridge. This only occurs when the player has not unlocked all of the islands, although only the bridges to Alderney and Algonquin are blocked because the only way to Happiness Island is by helicopter or boat. Any attempt to cross these roadblocks will result in a wanted level of 6 stars.
On a normal gameplay, every time that the player makes a wanted level of 3 stars, the NOOSE will start deploying their vehicles to make a roadblock, which is generally composed by the vehicle that is pursuing (NOOSE Cruiser or NOOSE Patriot). When the same reaches 4 stars, there would be either Enforcers, Police Patrols or Police Cruisers, which the later two are only placed if the FIB is pursuing the player. As seen in GTA 2, there are various easy-to-be-rammed-through barriers.
Police Roadblocks reappear in Grand Theft Auto V, however they are slightly different. Sometimes with a 2 star wanted level, the LSPD will form roadblocks using their Interceptor units. On three wanted stars, Police Roadblocks are a bit different and much more challenging to predict. This is because one will eventually spot one Police Transporter blocking two lanes of the road, with the opposite side being able to easily pass. However, when a Police Transporter is spotted blocking the road, there will always be a Spike Strip after it, causing anyone to pass this "roadblock" to end up with burst tires and a terrible car performance. If the player does happen to pass a Police Transporter blocking the road, the lone officer occupying the vehicle will get in the van and chase the player. On stars four and five, NOOSE will deploy Police Riots to block the road.
Note that not all roadblocks are always the same. For example, for a basic roadblock, two police cars are placed perpendicularly on the road, facing at the same orientation, while in another circumstance, a police car would be oriented straight to the road, surrounded by some traffic cones and some police officers ready to shoot the player. Unlike former games, any police officer will get in the vehicle that was set on the roadblock if the same fails to stop the player.