A safety car period exists to allow marshals to work in safety, but its effect on the competitive order is dramatic. It changes the value of everything a team has built up.
Gaps built over many laps disappear
Under neutralisation the field circulates slowly and closes up behind the safety car, so a lead measured in tens of seconds collapses to a car's length.
A team that has managed tyres carefully to build an advantage loses that advantage entirely, through no error of its own.
This is why drivers so often sound frustrated on the radio at the moment a period is called, regardless of what caused it.
The cost of a pit stop falls sharply
The time lost in a stop is measured against the cars still circulating. When those cars are running slowly, the relative loss shrinks considerably.
A stop that would have cost a driver several positions at racing speed may cost almost nothing under neutralisation, which makes it very attractive.
Teams that have already stopped gain nothing and lose their advantage, so the timing of an incident distributes fortune arbitrarily across the field.
Everything on the car cools down
Tyres, brakes and the power unit all operate within temperature windows, and slow running takes all of them below their working range.
Drivers weave and brake hard to generate heat, which is why the procession looks erratic. The tyres in particular need surface temperature restored before racing resumes.
Cooling is uneven across the field, so cars restart with quite different levels of grip depending on their tyre age and how effectively the driver warmed them.
The restart concentrates risk
Cars are close together, tyres are below temperature and drivers are competing for position immediately, which combines the three conditions most likely to produce contact.
Braking distances are longer than the drivers are accustomed to, and a car that has warmed its tyres better can close on one that has not with little warning.
Series therefore regulate the restart procedure closely, controlling where overtaking may begin and how the leader must control the pace of the queue.
Why virtual neutralisation was introduced
A virtual safety car requires every driver to run to a fixed slower delta time without physically bunching the field, which preserves the gaps between cars.
Because positions and intervals are maintained, the strategic upheaval is much smaller, though the reduced cost of a pit stop still applies.
It gives race control a proportionate response for incidents that need caution but not a full deployment, which reduces how often a race is reshaped by chance.