Biker Police are the only police force around the state of San Andreas that are consistent in all areas. (e.g. Country/Desert Police are found in respective areas and each city has a different police force) They are dressed in black with white helmets and are armed with Nightsticks and 9mm Pistols.
The Biker Police ride HPV-1000 Police Motorcycles. These are fast, agile and maneuverable. However, it is easy for the Police Officer to be knocked off the bike so that is a tight disadvantage.
However, due to the fact that the officer is out in the open he can (and under all circumstances) will fire it at you from his bike. He can also be shot due to the open bike.
Biker Police behave like all other Police, and will brandish a gun if you brandish one, the only extra behavior perk is that they will shoot you from their bikes regardless of your wanted level. Biker police usually chase you when you have a 1-2 star wanted level. They will more often than not back off after you get too many stars.
Vice City Stories
In Grand Theft Auto: Vice City Stories, Biker Police are pretty much the same as in Grand Theft Auto: San Andreas, except they ride a VCPD Wintergreen. They wear helmets, and wear regular police uniforms. They will only chase you at a 1-2 star wanted level, until faster, stronger, and all around better Police Cars arrive to chase you.