Update: Parmer / IH35 Diverging Diamond Intersection

Written by Pat Pitt

July 13, 2022

You may have thought that this amazing – and at first confusing – intersection opened back in 2021, and it did become “driveable” then. I was worried then about the difficult-to-see lane and stop markings, especially the stop llines because they were so hard to see and because they are staggered at the stop lights to account for the angle the crossing lanes make with each other. But the official ribbon-cutting was held on 22 June, and by this time all lanes were resurfaced and lines were repainted, making them much easier to see (unfortunately they’re already starting to fade from all use and “dirt”). As you can see in the picture, where the Eastbound and Westbound sets of lanes cross one another at an oblique angle on either side of IH35. The “stop lines” – marking where to stop when the lights are red – are staggered to allow as much forward progress as possible.

Thus the cars in adjacent lanes are lined up unevenly, which is an “unnatural” situation. The lines in your lane tell you where to stop, and if you go past your line only a short distance the front of your car will be in the closest lane coming from the opposite direction. I’ve seen a wreck caused by this staggered lineup (approaching cars may be out of sight at the time you stop).

This configuration allows the intersection to be controlled by only four sets of lights: The three at the crossing lanes on each side of IH35 allow traffic to flow either east or west, and the flow allows left turns with no stopping. You’ll probably be able to tell how much faster the traffic can travel through, and the average time to get through the intersection has decreased significantly. The other control lights control IH35 access road traffic making a left turn onto the Parmer lanes or making a U-turn back onto IH35.

The most aggravating change is caused by not being able to go through the intersection on the IH35 access lanes. These lanes ONLY turn left onto Parmer, so if you’ve made the wrong assumption you’ll find yourself either on Parmer going away from where you want to be or making a U-turn and back onto the access road in the opposite direction. To go straight through the intersection on the access road requires staying in the Parmer bypass lane and going under the Parmer bridge, then merging onto the regular access lanes on the other side.

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