You probably won’t notice them right away in 2004 vehicles, but a couple of telltale alerts or labels somewhere on the dashboard or around the ceiling of these newest models are the first signs that new safety equipment is on board.

Starting with the 2004s, at least one new safety item is required by the National Highway Traffic Safety Administration to be phased in on all passenger vehicles: Smarter front air bags designed to minimize the risk of injury and death to front-seat riders, particularly small-statured adults, the elderly and children, during a frontal crash.

The 2004 model year also was to mark the start of a government-required phase-in of tire pressure monitors on new vehicles to alert drivers of significantly underinflated tires.

But in late summer, a federal appeals court rejected the government’s plan to allow carmakers to use an indirect kind of tire pressure monitor if they want. Until the issue is sorted out, no NHTSA regulation mandating tire monitors is in effect, a NHTSA spokesman said.

While there’s no specific government requirement for side curtain air bags to provide head protection during side crashes, more automakers are adding these air bags to their new models.

Typically, curtain air bags provide protection for outboard riders in the front and second rows. But some go farther, extending far enough to provide protection for all three rows of seats.

Examples in the new model year: The 2004 Nissan Pathfinder Armada, where the curtains are standard and cover all three rows; 2004 Ford Freestar minivan, where the curtains are optional and cover all three rows, and 2004 Cadillac SRX, where the curtains are standard and cover the first two rows of seats.

NHTSA spokesman Tim Hurd said automakers find the curtain bags can do more than provide protection in a side crash. They also can be helpful in injury protection during rollover crashes and can even help keep riders from being ejected in such crashes.

Similarly, even before the NHTSA mandate about so-called advanced air bags went into effect this fall, many automakers already were adding these air bags to their vehicles. So, the 2004 model year marks the start of a final, industrywide ramp-up of this new technology.

Indeed, by the 2007 model year, all passenger vehicles are mandated to have advanced frontal bags.

These advanced air bags follow years of study that showed while frontal air bags were credited with saving 5,300 lives between 1986 and March 2000, they also could be lethal to smaller-sized people, including children, small women and the elderly, in some circumstances.

Specifically, NHTSA said more than 150 people, most of them children, had been killed by air bags over the years.

Researchers put some blame on people being too close to the bag when it deployed. But early frontal air bags also were designed to meet government requirements to provide protection for a 50th-percentile male who is unbelted during a car crash.

Therefore, automakers had to make sure their air bags deployed quickly enough and with enough force to give the requisite protection for a sizable male body not held in its seat by a safety belt.

Now, NHTSA requires a battery of new tests to make sure the advanced air bags take into account other people, too. The tests are done using a family of crash test dummies representing 1-, 3- and 6-year-old children, a small, 5th percentile female as well as the average, 50th percentile male.

NHTSA doesn’t tell automakers what to do to lessen the air bag danger to these smaller occupants while still providing protection to a man. But automakers’ efforts to make advanced air bags can focus on a couple approaches:

One involves turning off the frontal air bag entirely for the front passenger if a weight sensor or other type of sensor detects a child or child-sized person is in the outboard front seat.

In this case, somewhere in the dashboard area, the driver will see an alert telling him or her that the front-passenger air bag has been deactivated for the time being.

A second approach is deploying the front air bag in a way that’s less likely to cause harm to an occupant who’s sitting out of position in a seat. An example is to install dual-stage inflators in the front-passenger frontal air bag that provide for a lower-level air bag deployment when a crash is not that severe.

Note, though, that despite the arrival of the advanced air bags, government officials continue to urge that children under age 12 ride in the back seats of vehicles, where they will be safest.

Even without a government mandate, many automakers are providing tire pressure monitors on their 2004s.

For example, DaimlerChrysler’s Chrysler Group is largely unaf

fected by the court wrangling on the tire monitors, spokes woman Ann Smith said, because the automaker’s monitors do not check tire pressure indirectly.

Rather, monitors on the 2004 Jeep Grand Cherokee, for instance, determine the actual pressure of each tire via a sensor attached to the wheel rim, set flush against the tire.

A radio signal emitted from the sensor relays a tires pressure to a central receiver. If a tire is found to be significantly underinflated, a light and warning sound inside the van alert the driver.

Tire monitors became an important safety issue after publicity about Ford Explorer rollovers in 2000 put tire safety in the spotlight.

And a NHTSA study showed one-quarter of cars and one-third of trucks and sport utility vehicles were being driven by consumers with at least one tire significantly underinflated.

Indeed, the Rubber Manufacturers Association has found it’s more likely for a U.S. driver to have a clean, washed car than he is to check the pressure in his tires correctly.

Remember that even a tire pressure monitoring system will not warn a driver that a tire is bald or badly worn. And a tire monitor doesn’t substitute for regular tire maintenance and care.