In April 2024, Tucson made 10 intersections with two left-turn lanes arrow-only from 7 a.m. to 7 p.m. The other 44 still let drivers turn left on a green ball, yielding to oncoming traffic.
The 3D Corridor Explorer puts all 54 of these intersections in one interactive scene. Move from one intersection to the next along each corridor, sit in the driver's seat of the outer left-turn lane to see how an opposing left-turning truck or SUV can block the view of oncoming cars, and switch an intersection between arrow-only and yield-on-green phasing to see how the turns change.
Each intersection shows its own crash history from Tucson Police records, from 2018 through September 2026, along with an estimate of how many daytime left-turn crashes arrow-only phasing might prevent there.
What the data shows
- Daytime crashes fell 86%: At the 10 converted intersections, daytime left-turn crashes dropped from 7.7 to 1.1 per intersection per year. At the 44 intersections that kept yielding on green, they held at about 3.2.
- It's the phasing: At night, when the same 10 intersections still yield on green, left-turn crashes didn't fall.
- Night is the remaining gap: The converted intersections now average 3.4 left-turn crashes a year in the 12 night hours, against 1.1 in the 12 arrow-only daytime hours.
The full report covers the methods, a citywide map, and a ranked list of the intersections where the same change could prevent the most crashes.