It is the natural reaction of any motorist when they see a police car in their rear-view mirror to glance down.
Even if you know you have done nothing wrong, almost every driver will take that quick look at their speedometer to make sure.
As they cruise along the A9, Sergeant Chris Murray and Constable Chris Donaldson know they have this effect on other drivers.
After all their huge BMW X5, decked out in full Police Scotland livery, is not a discreet vehicle.
And nor is it supposed to be – a big part of road policing, as Sgt Murray explains, is to be a visible presence on the roads – and especially key routes such as the A9.
He said: “It’s certainly not our aim to be sitting at the side of the road and trying to catch people out.
“It’s about trying to influence driver behaviour. It’s about just being visible.
“Being here on the road has an influence on everybody round about us.
“Everybody will look at their speedo, they will probably drive a bit better when they see the police.”
He accepts that does not work on everyone, with an element of enforcement necessary, particularly he says in areas where there have been complaints about speeding, around schools for example.
However, on this day, like so many, Sgt Murray and Constable Donaldson are on the A9.
The north’s road policing unit covers the entire Highland region as well as the Western Isles, Orkney and Shetland – and at the drop of a hat officers can be dispatched anywhere.
But on a routine basis they spend much of their time on the north’s busiest routes, such as the road from Inverness heading south to Perth, the A82 road from the Highland capital to Fort William, and the A96 route heading east from the city.
It is a fairly routine day but there are still things happening if you know where to look.
Pulling in behind a southbound goods lorry, the two eagle-eyed officers spot a brake light which is not working.
The vehicle is quickly pulled over and given a good once over.
The driver has a spare bulb in his cab and within minutes the problem is fixed and he is on his way again.
Sgt Murray said: “Doing this kind of thing we can check over a vehicle and advise them.
“There’s not many random stops, more often we see them and point them out.”
Later the two officers will spot a car in the centre of Inverness which has its rear wheels badly out of alignment.
The driver is initially flummoxed to see the blue lights go on – and she pulls over as if to let the police car past.
But when she has the situation explained to her she goes with the officers to get her car checked over at a garage.
Afterwards she is grateful to the police for spotting the defect.
In his regular day job Sgt Murray is responsible for setting out the plans for the rest of the roads unit, based on information and complaints from the public, as well as statistics identifying possible blackspots.
He said: “The guys are tasked daily with addressing our priorities on the road, which is road safety and our main priority is reducing road casualties obviously.
“So it comes from various different strands.
“We look at what caused fatal collisions previously, like drivers falling asleep at the wheel for example in heavy goods vehicles.”
While all this activity is ongoing, the dream situation for road policing officers is every motorist being compliant with the rules of the road.
He said: “The key thing is that if you’re driving legally you’ll have nothing to worry about and you’ll never come to our attention.”
