Stuck in traffic a few days back, my idle mind wandered to the technical feasibility of pervasive, real-time traffic flow monitoring, and how this information could be communicated and utilized.

Such perfect, real-time information could help to redistribute the roadway load for the benefit of all (or, more realistically, let the suckers boil in the midday sun while the information insiders zip around congestion points), reducing transit times and energy use, and perhaps providing emergency services with optimized transport mapping, improving their efficacy.

Something had to be better than the sparse, time-lagged reporting of the radio station, or blindly rolling down an onramp, curious why a string of cars were dangerously reversing up the shoulder, to find the entire highway at a standstill, as I had that Friday afternoon.

There are quite a few implementation options apparent to a traffic layman like myself: Cameras with AI counting cars and estimating their speed. Underground (or overhead) magnetic sensors, or underground weight sensors. Laser relays for single lane roads.

The basic problem with such solutions, however, is that they tend to be expensive to install and maintain, and from that they tend to be infrequently deployed, at best spaced at distances that greatly reduce their utility (e.g. "between highway marker 70 and 112 there is some sort of disturbance"). Add to that the communications network required to relay these telemetrics.

Having worked in the telemetrics/remote monitoring industry before (in the late-90s), I was contemplating how cellular data technologies were just become feasible for such remote monitoring communications when the thought occurred to me: Most every cell phone now is constantly communicating digitally with its base station. Further, every cell phone can be either triangulated to a location, or more recently knows its precise position with the use of GPS. A tremendous percentage of cars on the road have at least one cell phone in them, the phone company (or anyone listening in on the conversation) capable of tracking location and speed, easily overlaying that over a mapping system to determine roadway flow.

Imagine an entire roadway system that overlaid the millions of cell phones moving around, easily visualization slow downs and congestion. It would be similar to the medical procedure where they inject radioactive particles into a patient's blood system, determining flow throughout the body by measuring their movement.

It turns out that I'm not the first to think of this. A quick Google search upon getting home made it apparent that there are several commercial products that do something similar. Nonetheless I thought it a fascinating example of passive data collection, deriving secondary advantages out of widely deployed technologies like cell phones.