Tag Archives: Maricopa County

Description and history of the location of the Tempe crash

Comments from Reed Kempton, a Senior Planner with the Maricopa County Department of Transportation, late in the day on March 21. This is an addition to my earlier post about the crash. I thank Reed for his permission to post his comments, which originally appeared on the e-mail list of the Association for Bicycle and Pedestrian Professionals.

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I’ve been driving through this intersection in its various configurations for 50 years and bicycling here for 48 (Yes, I am that old!) and would like to address some of the questions and statements from the past couple of days. Refer to the Google link below and note the position of the large X in the median. One report indicated that the pedestrian stepped off the median into the car’s path about 350 feet south of the intersection near the top of the X in the northbound direction. If this is the case, the car would have just changed lanes and been moving into the left left turn lane. 125 feet further south makes more sense to me as the car would be moving straight and not yet reached the left turn lanes.

https://goo.gl/maps/YkNMUu1nYZp

>How many lanes of car traffic are there?

2 lanes southbound; 2 lanes northbound; approaching the intersection northbound adds 2 left and one right turn lane; both directions include sidewalks and bike lanes

>Why does the area have clear, solid, inviting pathways across a median, if people aren’t supposed to cross there?

A history on the Mill Avenue bridges over the normally dry Salt River can be read at the Wikipedia link below but here is a short summary. From 1931 to 1994, only one bridge existed. Southbound traffic used the bridge while northbound traffic drove through the river. When water was flowing, a rare occurrence for many decades, the bridge was used for one lane of traffic in each direction. There was an asphalt crossover located just north of the bridge. When the second bridge was added, a crossover was put in place to accommodate the potential closing of one of the bridges. The X in the median is intended to be used to move cars from one side to the other if a bridge was closed. What looks like a path, has vertical curbs and signs that say do not cross here. In 1999, Tempe put two dams in the river to create a town lake.

https://en.wikipedia.org/wiki/Mill_Avenue_Bridges

>How far is it to a safer place to cross?

The signalized intersection is 350 feet north. Ped access to the park below the road is about the same distance south. Just south of that is a shared use path along the north bank of the river. The Rio Salado Path connects to path systems in Scottsdale, Mesa, and Phoenix making it possible to travel significant distances without riding or walking on a road.

>A trail meets the street where there is no crosswalk and no traffic signal.

While it is pretty easy to walk across the desert landscape in this location, there is no trail meeting the street. There are numerous mountain bike trails east of Lake View Dr.

Maybe tomorrow we will be given more information.

Reed

The Tempe crash

The dashcam video in the recent Tempe crash which killed a woman walking across the street with a bicycle has now been released.

To me, it is quite clear that the human driver was dozing off or distracted and that the vehicle’s sensors failed to register that the pedestrian — walking with a bicycle broadside to the road, a very robust infrared and radar target, and crossing empty lanes before reaching the one with the Uber vehicle — was on a collision course. The vehicle had its low-beam headlights on when high beams would have been appropriate, the headlights were aimed low (probably a fixed setting), and the pedestrian’s white shoes don’t show in the video until two seconds before impact, that is, at a distance of about 60 feet at the reported 40 mph.

Braking distance is about 80 feet at 40 mph, and reaction time for a human driver adds about another 60 feet. An automated system with radar and infrared should have noticed the pedestrian sooner, had a shorter response time, and stopped the vehicle. Human eyesight is much better than a dashcam’s at night and the human driver might have seen the pedestrian earlier and avoided the crash if she had been paying attention. But also, the bicycle had no lights or side-facing retroreflectors which might have shown up much earlier and alerted optical or infrared sensors or a human driver, and the pedestrian somehow chose to cross an otherwise empty street at precisely the time to be on a collision course.

So, the human driver and vehicle’s sensors failed miserably. We can’t allow automated vehicles (and human drivers) to perform at the level shown in this video. We do need to make greater allowances for pedestrians, bicyclists, animals, trash barrels blown out into the road, etc.

Several people have offered insights — see comments on this post, and also an additional post with a description and history of the crash location.