David Zabulowski/AP Traffic backs up on westbound Interstate 70 during the morning rush hour in Denver, Jan. 9, 2017.

More than a third of Denverites say their commute has gotten worse in the last five years, according to a new survey by the global staffing firm Robert Half.

The national survey found that 20 percent of Denverites had quit a job because of a bad commute. It also asked whether employers were offsetting bad commutes by offering public transit benefits or flexible hours. Nationally, 57 percent responded "no."

"Now, with the employer and the employee market in Denver being so tight and unemployment being at such a low rate, it's more important than ever not only to attract employees, but to retain," said Karen Policastro, the firm's regional leader. "Commute is an issue and it's something that's on employees' minds."

"Commutes can have a major impact on morale and, ultimately, an employee's decision to stay with or leave a job," said Paul McDonald, senior executive director for Robert Half. "In today's candidate-driven market, skilled workers can have multiple offers on the table. Professionals may not need to put up with a lengthy or stressful trip to the office if there are better options available."

McDonald said companies can offer remote work options, flexible scheduling or transportation amenities to ease the stress of commutes.

The Robert Half project surveyed 2,800 workers 18 years of age or older employed in office environments in 28 major U.S. cities.

The cities where the most workers left jobs because of the commute are Chicago, Miami, New York and San Fransisco.