A contentious bill that would allow drivers to turn left during rush hour at two key Kapiolani Boulevard intersections on weekdays was vetoed Tuesday by Mayor Kirk Caldwell, an action that could lead to an interesting political showdown.

Bill 89 (2017) was approved 5-3 by the Honolulu City Council on March 28, and the veto could be subject to an override by the nine-member Council at its next meeting, April 25.

The measure could have a major impact on rush-hour traffic, not just for residents of the McCully and Ala Moana areas, but also East Honolulu residents who use Kapiolani Boulevard for their daily commute.

City Department of Transportation Director Wes Frysztacki warned Council members that allowing left turns during rush hour at the McCully Street and Atkinson Drive intersections would effectively kill a Kapiolani Boulevard traffic initiative in place since 1952 that institutes rush hour contra-flow lanes and “no left turn” regulations stretching generally from Date Street to Kakaako.

Looking at the bigger political picture, the fight over the bill provides a good indicator of rough times that lie ahead for Caldwell’s political agenda under the new Council leadership headed by recently reinstalled Chairman Ernie Martin.

Caldwell’s three-page veto message Tuesday said city attorneys determined the bill “violates the separation of powers doctrine and disrupts the balance of power” between the executive and legislative branches at Honolulu Hale. The Council is tasked with broad policymaking while the administration, through analytical and technical expertise, is supposed to carry out those broad policies.

The veto message also said that DTS needs to gather more data before it can determine that getting rid of no-left-turn signs and contra-flow lanes at the two intersections would be best for the area.

“Bill 89 would undermine the director’s authority and the collective expertise within DTS to locate, select and install traffic control devices,” Caldwell said.

But Councilman Trevor Ozawa, who represents the Kapiolani Boulevard area and has been pressing to get rid of the rush hour traffic measures for more than two years, said the time for study is over. He said he got assurances from DTS officials two years ago that there would be a pilot project only to see “nothing — all talk.”

During the March 28 Council meeting, Frysztacki urged members to reject the bill.

Left-turn prohibitions during rush hour along Kapiolani Boulevard at McCully Street and Atkinson Drive are critical for contra-flow operations to be done safely, Frysztacki said. “So if you pass this legislation, you’re ending the contra-flow operation.”

Killing the Kapiolani contra-flow program “may be a wise thing if we’re ever to extend rail along Kapiolani Boulevard, because those middle lanes would be occupied by columns at some point in the future,” he said. But DTS first needs to hold a pilot project of at least six months to assess the long-term impacts of eliminating the contra-flow program, he said.

Calling the contra-flow program “unnecessary and outdated,” Ozawa urged colleagues to support the bill. The left-turn prohibition prevents both his constituents and other motorists in the area from quickly getting home, to work or to a night out in Waikiki. Instead, they either illegally jump the traffic-coned area or legally make “jug-handle turns” through the residential neighborhoods to get where they want.

In November the McCully-Moiliili Neighborhood Board adopted a resolution supporting the bill.

The community wants to allow left turns at the two intersections only going westbound in the afternoon, Ozawa said, adding that he doesn’t see why the entire contra-flow program needs to end immediately.

Ozawa’s efforts to allow left turns have been stymied in the Council Transportation Committee. Transportation Chairman Brandon Elefante said he did not move out the bill because of the legal concerns raised by Corporation Counsel Donna Leong, as well Frysztacki’s issues.

But that changed when Martin replaced Councilman Ron Menor as Council chairman early last month. The new, five-member majority — generally regarded as less favorable to Caldwell’s agenda — pulled the bill from Elefante’s committee, enabling the March 28 vote.

Joining Ozawa and Martin in passing the bill were fellow members of the new, five-person leadership team: Carol Fukunaga, Ann Kobayashi and Kymberly Pine. Opposed were those not on the new leadership team: Elefante, Joey Manahan and Menor. Ikaika Anderson, the ninth Council member and also on the outs with the leadership, was absent from the March 28 vote.

Six votes will be needed to override Caldwell’s veto.

Martin, in a text message, said he’s inclined to hold an override vote if Ozawa wants one.