Barnyard wrote:...the real reason for the disappearance was the change in the federal length law.
Yes, one of many reasons.
Length laws were adjusted along the STAA National Network in 1982 favoring conventional tractors yet sales of the cab over still soared almost a decade later to nationwide truckload mega carriers like J.B. Hunt and Schnieder National. Retailer Wal-Mart was also growing its distribution network during that time, all three companies loyal at the time to Navistar International.
Even with the cab over being nimble and superior in manuverability for fleet operations, before the turn of the century, fleet operators eventually fell out of love because of design flaws, poor fuel economy directly related to poor aerodynamics, the unacceptable amount of lost driver time from injuries recorded from slips and falls, and a huge issue with driver retention. Company drivers started leaving in mass exoduses for carriers' with "hoods" in their fleet.
Truckload carriers traditionally have the worst percentages of driver retention or the highest turnover rate industry wide.
Truckload carriers eventually realized fleet operators with conventional tractor fleets boasted higher driver retention rates, a key ingredient of lower operating ratios.
Price per unit eventually exceeded a conventional tractor further making the COE less desirable. This pounded the last nail into the coffin of the cab over.
With economy, safety, price, and driver retention along with the original shorter concept no longer necessary on the NN, the cabovers' fate was sealed. Navistar International ceased production of the domestically sold 9600 series in 1999.
To my knowledge, there has been no revision to STAA federal length laws along the NN since 1982, revisited in 1992 for LCV and intermodal language, reinterpreted in 1994.