An alert for drivers who use the US-60 westbound lanes: the Mill Avenue entrance is closed through Saturday night.
The Arizona Department of Transportation is working with the City of Tempe to track changes in speed as drivers approach the Interstate 10 turn-off.
That spot is in the top three for crashes in the Phoenix metro area.
Engineers think speed could be a factor as traffic in the far left lane slows approaching another freeway while drivers coming off Mill Avenue tend to speed up to cross four lanes in time to make the next exit. Engineers say secondary crashes are an issue as well if other drivers aren't paying attention or can't slow down fast enough.
"The crashes are usually minor, they're not severe but they often lead to secondary crashes and usually occur on a pretty regular basis," said Scott Beck, a group manager of ADOT traffic systems management operations.
The closure will last four days but the study will continue for several months before any recommendations are made for traffic changes.
The detour is to use Rural Road to access the US-60.
Here are the top five worst spots for Valley freeway crashes between 2014-2016:
1. Northbound Loop 101 between Baseline and Broadway: 721 crashes, 0 fatalities.
2. Westbound Loop 202 (Red Mountain Freeway) between 32nd St. and 24th St.: 672 crashes, 2 fatalities.
3. Westbound US 60 between Mill Ave and I-10: 656 crashes, 2 fatalities.
4. Southbound Loop 101 between Broadway and Baseline: 449 crashes, 0 fatalities.
5. Westbound Interstate 10 between 16th St. and 7th St.: 419 crashes, 3 fatalities.
Take a look at the map below for a detailed look at the most crash-prone spots on each Valley freeway in 2016 alone.