A couple of weeks ago, California Highway Patrol officers were involved in a high-speed chase during the evening commute hour on busy Highway 99.

Reader Pat Longest saw the chase on TV and was troubled by something. Many drivers on the freeway barely reacted to the drama around them.

"I didn't see cars pull over and stop," she said. "They just kept on their merry way, perhaps a little slower for a few seconds."

The law says that when you see emergency vehicles approaching with lights and sirens, you pull to the right of the road and stop. That goes for freeways as well as city streets, officials say.

So, were those drivers unaware of the law? Or were they actually unwilling to inconvenience themselves to allow police to do their job?

CHP and police say there is a third possibility, a scary one.

Imagine yourself driving on the freeway. If you haven't checked your rearview mirror for a few seconds, you could be in for a shock when you do.

High-speed chases often roar up from out of nowhere on unsuspecting drivers, police say. One problem is that, at 65 miles per hour, sirens are harder to hear behind you.

"They may never hear the siren until we are right up on them," CHP Officer Mike Bradley said.

In the case of the Highway 99 incident, which happened the first week of January, officers were chasing a large Chevy Silverado.

Officers say their flashing lights can be obscured at times to some drivers ahead when there is traffic in between, especially larger vehicles.

All this is just another reason why the best and safest drivers are the ones who have their heads constantly on a swivel, scanning to the front, back and sides.

So, what do you do when you notice a high-speed freeway chase right behind you on the freeway? Police say some drivers instinctively do the worst thing possible: They hit the brakes.

Instead, you should hit the right blinker, so other drivers, including the police and even the bad guy (if he's paying attention), know you are trying to get to the right. Then you should switch lanes carefully, if you can. If you can get to the right shoulder and stop, that's the best bet.

By the way, officers are taught to stay in the fast lane and pass on the left during chases, no matter what the suspect does.

In the Highway 99 chase, officers got the guy by throwing a nail strip on the freeway that blew out his tires.

That brings up another safety issue. If you come up on a freeway crime scene with action ongoing, such as the moment officers were getting out of their cars to make the arrest, you should try to pull over and stop behind the incident, even if there are open lanes. That allows officers the space to do their job, and avoids putting you at risk.

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