FlyingForFun,
I'm amazed to hear of an aerodrome that allows a vehicle on a runway at the same time as an aircraft that close to landing. I'd love to see the risk assessment that allows this to take place.
There are tasks requiring a continuous run down a runway by a vehicle; friction measurement and taking readings of output from light fittings for instance, but surface inspections can easily be done in chunks between aircraft movements. We do 49 heavy jet transport movements an hour off our single runway and manage to squeeze 3 daylight surface inspections in per day without breaking any of the rules. We most certainly are acutely aware of the position of the aircraft in the vicinity of the runway and we share the same frequency so we know exactly what's going on. Hopefully crews are also aware of the instructions that we've been given by ATC, too. Our teams take pride in having a standard of RTF at least equal to aircrew and ATC.
When we do require a continuous run down the runway we co-ordinate with ATC to provide the necessary spacing. I'm not saying we get it completely right all the time but there's still enough safety margin to give us some leeway and not cause a go-around. VERY occasionally, our continued presence may result in such, but only because we're unable to vacate for a good reason, such as recovering debris for instance. In that case, ATC will issue a mandatory go-around instruction.
Cheers,
The Odd One