After years of tolerating potentially deadly heat on their routes, UPS drivers will finally get air conditioning in their trucks. The news comes as the delivery giant and the Teamsters union negotiate a new contract for 330,000 workers set to expire July 31, with heat protections a major issue as climate changes pushes up summer temperatures.

"Air conditioning is coming to UPS, and Teamster members in these vehicles will get the relief and protection they've been fighting for," Teamster general president Sean O'Brien said in a statement. "Today's progress was a significant step towards a stronger new reality for so many workers and their families."

Starting next year, UPS' package delivery trucks will come equipped with AC, the company and the Teamsters union announced. Older trucks will be retrofitted to allow AC, the company said.

"Where possible, new vehicles will be allocated to the hottest parts of the country first," UPS said.

The company will also install fans in the driver's cab and exhaust heat shields for the cargo area in non-electric trucks. Shields reduce the amount of heat passing from the truck's engine to the cargo hold, which can reach 140 degrees Fahrenheit on a hot day.

Dangerous heat for UPS drivers has been a major issue for years. The company is the only major delivery company to resist installing AC in its vehicles even as reports mounted of drivers falling sick from heatstroke and needing to go to the emergency room.

Last year, a UPS spokesperson told CBS MoneyWatch that installing cooling systems in delivery trucks was not "feasible" because of their frequent stops.

In a statement this week announcing the air-conditioning changes, UPS said, "We have always remained open to solutions that keep our employees safe on hot days. The Teamsters raised A/C as a top priority for their members, and the new solutions we've agreed to will improve airflow, temperature and comfort for our employees."

Air conditioning was a major issue in the current negotiations between the company and union. Workers are also seeking higher pay for part-time and inside workers, the removal of surveillance cameras in cabs and an end to a so-called two-tier pay system that allows newer workers doing the same work as older workers to be paid less.

A strike by UPS drivers and warehouse workers would be among the largest labor stoppages in recent U.S. history. The union's membership recently voted on whether to strike if no deal is reached by the time the current contact expires on July 31. Results of the strike vote are set to be released Friday.

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