Every other weather map answers the question what is it doing there now. On a long road that is the wrong question. Leaving San Francisco at eight in the morning you reach Salt Lake City after dark and Cheyenne the following afternoon, and what matters is the weather that will be waiting when you arrive — not the weather that is there while you are still packing.

So the clock runs. Position and time are locked together at your chosen speed, and every mile is read from the forecast valid at your arrival. Drive west at sunset and you chase the light; drive east and night falls early. The sky above the road is computed from the real solar elevation at that latitude and longitude at that instant, dimmed by the forecast cloud cover, so the darkness on the screen is the darkness you would be driving in.

The TripTik is the same idea flattened: the whole route left to right, coloured by the temperature you will meet, banded where rain, snow or freezing rain is forecast for the hour you pass through, and shaded where you will be driving at night.