PROFESSIONAL AND DEMANDING JOURNEYS

Some journeys carry consequences that ordinary ones do not. A booked slot that cannot be missed, a vehicle that will not fit everywhere, a customer waiting, hours that are counted. On journeys like these the question is no longer whether the satnav is any good. It is how several imperfect sources of information should be combined by the one part of the system capable of judgement, which is the driver.

Drivers who do this for a living rarely rely on a single device. They run a specialist system for the vehicle, a general mapping application for traffic and imagery, and their own accumulated knowledge of the roads, and they know which to believe when the three disagree. That is not distrust of technology. It is an accurate understanding of what each part can and cannot do.

The preparation that distinguishes a demanding journey is specific rather than general. Confirm the destination is where the postcode says it is. Look at the site from above and decide where you are entering and how you are leaving. Identify the two or three junctions where a mistake would be expensive, and know what the signs say at each. Note where the route commits you — the motorway junction after which there is no easy alternative for twenty miles.

Work out the fallback while it is cheap to work out. If that road is closed, what is the alternative, and does the alternative suit the vehicle? A plan made calmly at a desk is worth a great deal more than one made at a diversion sign with a queue behind you.

Live traffic is the most valuable thing modern navigation offers and the easiest to over-trust. It reports what other vehicles are doing now; it does not know about the incident cleared two minutes ago, and it cannot tell whether the alternative it proposes suits your vehicle, your hours or your load.

Used well, it is early warning. A delay ahead is worth knowing about long before you reach it, because it turns a forced decision into a considered one. Used badly, it becomes a series of hurried lane changes in pursuit of savings that never quite arrive. The professional habit is to take the information early, decide deliberately, and be entirely willing to stay on the original route.

The device supplies information. It has never once supplied judgement, and it is not going to start.

One thing this site does not do: it does not offer vehicle-specific legal routing. Nothing here replaces a specialist system built for the vehicle you drive, the operator's own instructions, the rules on drivers' hours, or the signs and restrictions you meet on the road. Those come first, every time. What the six principles add is the thinking that sits on top of them.