The confluence is a massive merging of 17 lanes of freeway into just 14 lanes. It passes through Diamond Bar and the City of Industry and ranks among the highest in traffic delays and truck accidents.
"This interchange, I don't think I have to tell you, had truck-related collisions in the confluence, at this point, about 50% or higher than the average state," Los Angeles Supervisor Hilda Solis said during a groundbreaking ceremony on Friday. "We are here to bring it down."
The 57/60 Confluence Project has been in the works for nearly 20 years but will officially enter its final phase of construction this month.
$218 million state grant includes funding for improving 57/60 Freeway interchange in Diamond Bar
The current issues that are set to be addressed include "lane drops," which lead to dangerous weaving between drivers.
The project will rearrange connecting ramps and add general use and bypass lanes to help alleviate congestion, improve road safety and air quality.
The changes will also affect nearby ports.
"Upon completion, this transformative project will substantially reduce traffic congestion and improve freight movement daily," said Rep. Judy Chu.
The total cost for the project is $444.12 million. It's partly funded by Los Angeles County taxpayers via the passage of Measure M.
"Anything good, you have to suffer a little bit of pain in getting through the process but it will be well worth it," said Monrovia Mayor Becky Shevlin.
The project is expected to be completed by July 2028.