Mayor Rahm Emanuel signed a five-year deal Monday with the CTA's construction and maintenance labor unions that trades cost-cutting work measures for a no-layoff guarantee.
Afternoon and evening shifts will now be paid with a "differential" fee, not overtime.
Officials say that the new contract will give them more flexibility.
"Obviously, we can do a lot more efficient work and less disruptive work if we can do more work on the second and third shifts, which this agreement will give us more flexibility in regards to," said CTA President Forrest Claypool.
The contract is expected to save the city $5 million per year in healthcare costs, and $1.5 million per year in other costs.