Rush hours in the jammed streets of Saudi cities give most people the chance to look around at other vehicles. In among the plethora of shiny new SUVs and smart limousines and sports models, there is a good number of mid-budget vehicles and, when they are permitted onto the city streets, trucks and delivery vans. Not all of these appear to be in the best condition and at one time or another everyone must have found themselves behind a truck or crew bus, belching black smoke.

Even new vehicles with catalytic converters will produce some pollution, not least when engines run at idle for long minutes at a time, as drivers wait for the traffic ahead to start moving again. Therefore it is understandable that municipal authorities should be seeking to crack down on vehicles that are not in prime condition.

However Makkah traffic department’s decision, on entirely acceptable environmental grounds, to ban expatriates from having more than two worn-out cars is puzzling. The official responsible for this decision, speaking to this newspaper earlier in the week, made it clear that this was not a move specifically against expats, but simply that they tended to have the oldest and most used vehicles.

All of which is fair enough. However the puzzlement arises because the Kingdom has a very efficient Motor Vehicles Periodic Inspection system. This means that every time anyone in the Kingdom renews their vehicle’s registration or sells or buys an automobile, the MVPI test is compulsory. There are now some 24 testing stations throughout the country, whose job is to assess the safety and road-worthiness of automobiles, vans and trucks.

Drivers have often complained that the checks done by these stations are in fact too strict. For instance, dripping oil beneath the car can lead to failure because it is assumed that there is a serious leak that must be fixed. It certainly seems that when it comes to the initial visual inspection, some testers are tougher than others. The subsequent automated checks on the likes of brakes and emissions are of course entirely objective.

The point is that every vehicle in the Kingdom is required to go through an MVPI and if its does not pass the test, is supposed to be fixed and represented for re-testing within 14 days. The penalties for failing to have a current MVPI decal on your windscreen can be severe, ranging from fines to the confiscation of the vehicle.

Now it is perfectly possible for an old automobile that is well looked after to be kept on the road for years, passing its MVPI every time. Indeed, there are car buffs in the Kingdom who collect old vehicles and submit them for regular testing, without a problem.

Yet if the Makkah traffic department is concerned at the environmental impact of old vehicles, it has to be because these vehicles are not properly serviced and maintained. And if they have not been looked after in an appropriate manner, then there is no way that they could have passed their MVPI. So what is going on here?

It seems highly unlikely that the MVPI stations, with their strict reputation for insisting on the highest standards, are suddenly falling down on the job. So the suspicion has to be either that vehicles are being driven around with no MVPI or that the sticker they display is in fact fake. The issue therefore boils down to one of enforcement. Police ought to be looking out for suspicious vehicles. Even if an automobile appears to be street legal, but is belching smoke or clearly poorly maintained, law officers have good grounds for believing it has no current MVPI. They should stop the driver and investigate.

As the traffic camera system expands, it will be possible for an image of a vehicle’s registration to be checked against the MVPI database and a traffic violation notice issued automatically if it does not have a valid test. This will be a further powerful tool in the hands of the authorities. Yet the existing MVPI process already offers an effective way of keeping polluting and dangerous vehicles off our roads. Banning anyone from having more than two old vehicles is not really the issue. The point is that every vehicle, however old simply has to have complied with the law in terms of the appropriate testing and to have been passed as safe and roadworthy. The resolution therefore rests in the enforcement of entirely adequate regulations.