The city's Dept. of Buildings already has banned two tower-crane models built in the 1970s and 1980s—36 units in all—after "they were identified to have documented performance and safety issues," according to the department. Two such cranes erected at the World Trade Center site dropped loads due to faulty hoist drums, the city determined. The Link-Belt and Favco brand units are no longer supported by a manufacturer. Cranes Inc. owns five of those units, one of which is now working across the Hudson River, in Hoboken, N.J.

Machinery bans could hike construction costs, Weiss noted. For the 36 banned cranes, "the industry just doesn't have the money to purchase $120 million in new cranes," he said. Further, a new tower crane of the same size rents for $80,000 to $100,000 a month, while the older units rent for $35,000 to $40,000. "The cost impact to the steel industry has been dramatic," Weiss said. "It's name-your-own-price now in New York City."

On the other hand, keeping vintage cranes alive also can produce diminishing returns, Wiethorn acknowledged at the meeting. "Life expectancy is directly related to economic value," he said. "With age, it is going to cost a little bit more." Attendees asked him at what age it makes financial sense to scrap a crane, and Wiethorn replied, "You'll have to read the study, but it is getting into the 30s and 40s."

Flight Recorders Considered Risky

Crane owners, manufacturers and insurers also debated the question of whether machines should be equipped with black boxes that record lift data, which is a notion that is part of the pending legislation in New York City.

Currently, no standard yet exists for these devices. Tadano rough-terrain cranes, for example, record the past 50 lifts, with such details as date, time, load moment, boom length, boom angle and outrigger placement, among others. They also record the 10 heaviest lifts. However, Tadano does not provide the user access to this information. Some brands record even less data, if any.

Crane owners said they didn't want the liability of a black box, even if the data could exonerate them in court.

Bob Moore, chief legal officer for NationsBuilders Insurance Services Inc., said that a flight recorder, similar to what aircraft use, would be a reasonable solution if it were limited to just a few hours of data and handled by a trained professional, to avoid tampering.

"You want to have the data so you can have an accident investigation," he said.