Q: Subway trains have advertisements touting the system’s hightech cars, but I’ve seen the cards on cars that are definitely not hightech. Is this a joke? If it is, I’m not laughing.

A: You may be referring to an advertisement that can be seen throughout the system, but was photographed for The New York Sun on an E train that had no air-conditioning. The effort to upgrade the aging fleet of subway cars has led to stark differences between certain lines. The ad campaign is an effort to soften that distinction through humor. For people who ride the older cars, such as the E train’s R32, which was built in the 1960s and features stainless-steel-ribbed siding, the signs do little other than inspire “car envy.”

Another reads: “You’re now standing in one of our new high-tech cars. If you’re not, we will talk to the person who put this card here.”

The process of upgrading the 6,221 cars in the fleet began when the first capital plan was introduced in 1982. It took until 1992 to bring all the cars up to the Metropolitan Transportation Authority’s standard of good repair, which included refurbishing the oldest cars, including the R32s.

The subway cars in the system’s aging fleet are meant to last 40 years and have an average age of about 21 years, according to the MTA.

All the cars will eventually be replaced with the current mode of computer-equipped trains, despite a setback with the MTA’s $1.14 billion order for 660 of the most high-tech cars, the R160s. Because the French manufacturer, Alstom, has had trouble finding parts, the order has fallen behind schedule. Nonetheless, a prototype is scheduled to arrive September 16 for around-the-clock testing over the ensuing 14 months. Those new cars are meant to replace the oldest cars on the system’s “B division” which are the wider cars on, for example, the A, C, and E lines.

Likewise, the MTA, which is working to complete the computerized L line next year, plans to buy 47 new R142 cars – as seen on the nos. 2, 3, 4, 5, and 6, and L lines – in the next five years, for $76 million, to convert the no. 7 to a computerized line.

The greatest benefit of new subway cars often goes unseen. The MTA says the 1,030 R142 cars currently in service will travel about 200,000 miles more than the fleet of 594 R32 cars before breaking down. Until the cars from Alstom come online in October 2006, though, passengers on A, C, and E trains will have to endure reminders of their low-tech environs.