All the ships of the BSG universe employ some variety of Reactionless Thruster for sub light or Probe Speed speed maneuvering. Some vessels, like shuttles and most Cylon attack craft, are ONLY sub light capable.
Sub light speeds are variable from near zero, allowing delicate docking maneuvers, to many hundreds of thousands of metrics per centar. A ship’s top speed using its sub light engines can vary depending on the size of the ship’s engines, the power available and the mass it is carrying. Freighters and other ships intended for massive cargoes, can carry vast amounts of weight and still obtain reasonable STL speeds.
Ionization Trail. Virtually all reactionless drives leave a trace of their passage in the form of a faint Ionization Trail. This effect dissipates in a few centars and becomes undetectable. But during that time period it is possible, though difficult, to detect a ship’s passage and potentially plot a course from it. Also, the immediate area of the Ionization Trail, directly behind the ship’s thrusters, is not a good place for another ship to be. The effect can play havoc with sensors making safe navigation difficult. The effect of this Ionization ‘wake’ also impacts the sensors of the ship looking backwards, through its own trail.
NOTE: Cylon Baseships, Attackships and Patrolships, as well as Vilium ships use a gravitic based drive that leaves no ionization trail.