We don’t have to widen roads to improve traffic flow. We can upgrade traffic signals instead, using computer systems which optimize the flow of cars through intersections. We can save a ton of money in the process.
City streets are different from highways because of cross streets and pedestrian crossings. A common belief is that traffic always moves more quickly if there are more lanes. Not true. Adding lanes creates longer delays at intersections because of jam-ups created by the greater volume of cars and the greater distance that pedestrians have to cross.
Widening has limited value and can even be counterproductive. In the plan for the Broadway widening, the original eight-lane configuration would have been slower than the current six-lane plan, largely because of intersection delays, as determined by computer simulation. Even with six lanes, drivers will spend nearly half their time at red lights in that area, according to measurements by the city of Tucson and outside consultants.
Going fast doesn’t do you any good if you keep getting stopped.
To increase the capacity of a road, the intersections are the place to start. We can do that with real-time computer systems, which monitor traffic flow from all directions, and adjust signal timings dynamically. These systems, known as Adaptive Traffic Control, are a major improvement over ordinary synchronization. For drivers, this means less time waiting at red lights.
Optimizing signals is a game-changer. This is no longer a battle over reducing congestion vs. preserving neighborhoods. We can do both. Traffic engineers are implementing these systems in cities throughout the country. They are well-established and reliable, and can produce greater gains than widening, at a fraction of the cost.
We’re talking a couple of million here instead of the $70-plus million being spent to widen Broadway. This eliminates waste of taxpayer money, frees up funds for other transportation-related purposes and avoids the years of slowdowns due to road construction projects. The smoother ride produces less air pollution because there’s less starting and stopping. There also less of the heat island effect because there’s less pavement. Maybe Tucson wouldn’t be the third-fastest-warming city anymore.
Fortunately, Tucson’s transportation department, with new leadership, sees the value of these systems. So we can expect better traffic flow with less widening and less destruction of adjacent buildings, which goes along with the widening.
The controversial Broadway widening had other issues as well. Studies showed essentially no increase in traffic in 20 years, for several reasons. Population growth had shifted from the east side to the northwest and the Barraza Aviation Highway provided an alternate route for drivers from the southeast side.
That area also has an unusually large number of pedestrian crossings, whose random nature affects the synchronization of timed signals. If not handled properly, this factor alone reduces the road’s capacity more than any gain to be achieved by widening, according to data in the project’s design document. Adaptive signals can make adjustments to respond to this.
The move toward adaptive control is part of a broad national change in thinking about urban transportation. Planners recognize that alternate modes of moving people can be less expensive while reducing impacts on neighborhoods, businesses and historic preservation. In metro areas such as Phoenix, light-rail systems are well-received by riders, reducing traffic volume on regional freeways. Another option is bike paths on residential streets, giving riders a safer and quieter way to take short trips.
Widening a city street is an expensive way to increase its capacity, and not a very effective one. Upgrading signals is much less expensive, and far less intrusive, than widening.