Returning to a parked car and realizing it has been towed ranks up there among the most dispiriting experiences in driving. It usually means a disruption in the daily schedule, calling a friend to help with transportation — and a fat bill besides, payable in cash only.

And now it appears those bills could have been inflated, if not for an inquiry by Star-Advertiser writer Rob Perez that nudged unaware city officials into action to stop the practice.

The irony, and the reason the city must ramp up its initially lax oversight: The company won the lucrative islandwide contract on the basis of more favorable rates to those paying the penalty for the tow.

The contractor, Leeward Auto Wreckers, took over police-initiated tows on Nov. 1, and within a matter of weeks the irregularities have come to light.

After at first defending its interpretation of the contact documents as being a legitimate means of making the deal more viable financially, company executives acknowledged the unauthorized markups after being called into a meeting with the city.

Leeward Auto was charging a $65 hookup fee, compared to the $60 offered in its pact with the city, as well as $7.50 per towed mile, rather than the agreed $7 rate.

Those overcharges came to light in a Star-Advertiser review of about 100 accident-tow invoices.

The company clearly needed an edge to compete in the city’s recent overhaul of its towing contract. Oahu had been sectioned previously into 13 zones, with various companies competing for each exclusive contract. Leeward Auto had no experience handling the Honolulu Police Department-ordered tows.

Additionally, the contract marked a complete departure from the city’s prior, competitive practice. City officials had the idea — and it seemed rational enough — that a unified contract would address the complaints lodged by motorists about inconsistent service among the handful of vendors providing the towing service.

The city’s weak response to the Leeward Auto revelation was that it had not received any complaints of alleged overbilling and so had not audited the contractor.

But given the newness of the contract scope and the vendor, officials should have monitored the launch keenly from Day 1, instead of relying on public informants: What motorist could be expected to be aware of the correct rates?

Further, the entire category of service should have been high on the city’s radar. Past problems had provided ample reason for reform, including the disclosure by the Star-Advertiser two years ago that the vendor handling Oahu’s busiest zone, Stoneridge Recoveries, was under criminal investigation by the state’s insurance fraud unit. Stoneridge ultimately lost the contract, but the criminal investigation continued, with a decision on pursuing charges now pending.

Honolulu should have learned from that experience and now must ride herd on Leeward Auto.

Officials said they will compel a complete accounting of all charges for police-initiated tows, a plan to refund any overcharges and a plan to ensure compliance with contract terms.

That appears to be the right track to follow. No future taint should be tolerated, and any overcharging beyond the agreed fees would be a breach of the deal.

Towing is one of the necessary duties of municipal management, to enforce parking restrictions that enable traffic to flow. Most taxpayers realize that, but they have a right to demand fair treatment.

The city’s part of the bargain is to see that they get it.