Give Way

“Okay, let’s go over how the traffic priority controls work. You can up-priority by paying a small fee, with a promise to pay more if your higher priority becomes relevant. The fee goes to us, the later charges to every vehicle that’s inconvenienced by yours. Or you can down-priority, which is free, but nets you a small payment every time the road-grid can pick you to ‘lose’ rather than another vehicle.

“But people don’t understand how the vehicle priority algorithm works underneath.

“It doesn’t affect vehicle speed, or routing, or any such. We can’t run vehicles efficiently at multiple speeds over the same roads, after all. No, what the traffic priority setting does is affect the way the road-grid handles resource-contention decisions where two vehicles require the same resource – odoblock, say – simultaneously, and resolving this deadlock require that one vehicle be selected to ‘lose’, which we define as a set of parameters including increased travel time, increased travel cost, vector changes outside the passenger comfort envelope, user preference deviations, and so forth. In those cases, the lowest priority ‘loses’, and where multiple vehicles share the same priority, a random function decides the loser.

“That’s a simplification, but it’s close enough to true. It’s most visible with emergency response vehicles, which naturally have a hard-coded top priority, but if you carefully study the patterns of traffic around some other vehicles over time, you can see the algorithm at work. Sleeper cars and fragile cargoes, for example, have their comfort envelopes weighted higher so other vehicles ‘lose’ to them when a maneuver is required. Bulk freight without deadlines is usually deprioritized for the potential savings, so statistically speaking, robotrucks ‘lose’ more than regular traffic.

“So why do people think that these don’t do anything?

“Well, how often do you think the road-grid system needs to make resource-contention decisions?”

– Eimil Murianos, odocorp engineer, IBC live interview