Safety First…Second, and Third

September 20, 2016 — Improving safety is a key benefit of making real-time, predictive, traffic signal information available to road users.  It is also Connected Signals’ first and fundamental priority. We never deploy functionality that we believe makes road users less safe. Period. Quite the contrary: We invest significant design and testing effort ensuring that signal information is provided in non-distracting ways that do not encourage unsafe behaviors.

For example, when our EnLighten® smartphone app was first released, it continued its red light countdown all the way to zero. Discussions among our developers, testers, and municipal partners made it clear that drivers might simply drive off when the countdown hit zero and without actually looking at the signal itself. We responded to this completely unacceptable outcome by stopping the countdown at five seconds, at which point we sound a chime to alert drivers to focus their attention on the roadway and get ready to drive.

Another example involved the introduction of indications as to whether drivers would arrive at the next signal while it was green.  We were concerned that this information might induce people to speed up to make a light they were told that they were going to miss. Since we had two groups of drivers–those with iPhones and those with Android devices–we were able to deploy the new functionality to only one group and observe its effect on behavior. We found that drivers not told that they would make a green light ahead of them by and large sped up, while those who knew they’d make the light at their current speed did not. We also found that telling drivers they’d miss the next light tended to cause them to slow down, not speed up. A larger study is currently underway in San José to determine whether this effect occurs more generally.

Finally, we are currently experimenting with a speedometer display that shows red and green arcs  (bounded by the speed limit) indicating speed ranges that will miss or make the next light or group of lights. Arriving at red lights is inherently dangerous. In the US, there are a quarter million red light incursion accidents a year, with 40% resulting in injuries or death. By helping drivers stay in the green wave, and by giving them advance warning to slow down when they will arrive on red anyway, it may be possible to reduce these numbers. The San José study will help to determine whether this is the case. Individual users are already reporting that seeing the speedometer needle near, or above, the top of the green indicator motivates them to slow down. They also report that the fact that the speedometer visually indicates when they are speeding moderates their driving. The data are not all in yet, but early indications are that safer driving can result.

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