As someone who pays a great deal of attention to traffic technology , I have in general been pleased at the additional information one gains as a result of the travel time indicators I have seen for about a year on the highways here in the Portland area. On a conceptual level these machines are fairly simple—pick a major interchange and tell a driver how long it will take to get there. The reference points chosen are fixed, and they update every minute or so. For the astute and alert driver who pays attention to the signs, they offer enough information for it to be possible to amend one’s expectations and occasionally one’s route. A substantial difference in time between two route alternatives can allow one to change course instead of being stuck in traffic without warning. Being someone who particularly hates to be stuck in traffic, this is an immensely favorable outcome, given the possibility at mitigating the frustration of being stuck without moving, I will take it .
In order to effectively deliver this information, a lot of data computation is necessary. There are many ways that one could tell how long it took a given vehicle to travel from one point to another a few miles away. One could collect the speed information of motorists and convert it into time, aggregated over the cars on a roadway that pass a given point. If one had the ability to read license plates one could collect timestamp data of a vehicle at one point and then show its arrival at another point, aggregating enough to provide a particularly accurate time for vehicles, but one that would be extremely data-intensive, and one that would be extremely personal as well, given that it could serve as a way of providing notice of prolonged speeding. It is unlikely that Oregon’s system is anything this precise, as it tends to show minimum times assuming a speed limit drive along a given route, which can then be corrected for drivers that go a bit over the speed limit like myself. It is far more likely that the information from the displays that give the advisory speed are what feed into the speeds that convert into the travel times people are looking at, although many of the places where this information is recorded do not appear to have any displays at present. Regardless of how the information is gathered, the display system needs something to monitor the speed of vehicles at given points and then be able to convert that data into the amount of time spent traveling from point A to point B. I would be curious to know exactly how this is done.
What is the main benefit of the time travel displays, assuming they are working correctly? For one, the main variable in people’s definition of travel comfort and travel distance is not pure mileage, but time. An example should suffice. When my mother comes to visit town, she usually stays with a friend of mine in rural Clackamas county, and I usually stay over at that time as well to spend more time with my mom, even if it requires very lengthy driving to and from my work on the other side of the city. Although the travel distance in statutory miles is roughly the same between my morning and evening routes, my subjective impression of the ride is far different. In the morning, there is much less traffic, and my mind is free to ponder the fog on the hills and the many different shades of gray of Portland life , and my travel experience is conducive to reflective if melancholy poetry over the course of the hour it takes. On the other hand, my drive home takes about twice as long and includes harrowing trips through a tunnel and over a bridge, lots of stop-and-go (mostly stop), and is a considerably less pleasant travel experience despite the same mileage. Knowing which of the two main routes to go, which must be committed to very early in the trip, is a big factor in making a stressful trip at least a little bit less stressful.
I am sure a lot of people agree with me that they appreciate having more information, especially if it is consistent and accurate enough to lead to correct decision-making. In my driving experience, the displayed times around the highways are accurate enough for me to know how long it will take to follow a particular route, and are usually timely enough to allow me the opportunity to take a different among the options from a given highway. The real determining factor for me is knowing the state of the highways so that I start off in the right direction. To be fair, this is a task that would be beyond a traffic system unless it was present on the roads with highway entrances before those entrances, but still, it is interesting to see the development of technology to make travel more pleasant for motorists, and I am always interested in seeing what new technologies are developed in the course of time, especially those that are of benefit to my own personal life.
 See, for example:
 See, for example: