Should ABS brakes, leave marks on the road ?
The simple answer should be 'no', because in principle, skid marks are a by-product of what an ABS system tries to prevent - the locking of the wheels.
Braking power is fully dependent on how much grip (friction) the (usually front) tyres can generate
If you press hard on the brakes in a car without ABS, the tyres can only take so much stopping force (friction) before they 'lock up'. This is where the car is still moving, but the wheels are not - hence rubber being dragged along the road and leaving black lines.
ABS works by gripping and un-gripping the brakes in rapid succession, allowing braking to still happen, right on the verge of 'lock up'.
ABS leaves marks that are lighter and therefore harder to detect. Since these marks are lighter, traffic conditions, weather and rain can wash away these marks easier than non ABS skids. Therefore, extra care is necessary when examining the scene where ABS applies.
Another important difference between ABS and conventional tire marks is in their pattern. Conventional marks are solid continuous streaks if not interrupted by pedal pumping or irregularities in the road surface. They often begin and end abruptly in addition to their prominence. ABS on the other hand may follow an intermittent light and dark pattern. The reason for this is that sensors relay wheel speed information back to the microprocessor in the vehicle's computer. There is a slight delay in the feedback system which allows the wheel to cycle from higher to lower brake force, resembling a consistent cyclical pattern. Flat spots are less likely on ABS since the tires are less likely to lock. Therefore, flat spots will not be evident unless the vehicle has spun sideways.