The Honolulu City Council this morning passed a bill that would ban the use of handheld cell phones while driving.

Motorists could still use their phones via hands-free technology.

Mayor Mufi Hannemann has said he supports such a ban. If he signs it, the law would take effect July 1.

Maj. Thomas Nitta, head of the Honolulu Police Department's traffic division, said some details on how the law will be implemented need to be worked out. However, it's likely the fine for a first violation would be between $20 to $100.

The measure was proposed by council members Rod Tam and Donovan Dela Cruz after Hannemann vetoed an earlier ban that included text messaging and playing video games.

Hannemann and Honolulu police said the law would be unenforceable since officers would have to determine what the driver was doing.

Under the new bill, an officer only needs to see a driver holding an electronic device while driving to issue a citation.

The bill exempts emergency workers if they are in the performance of their duties.