IEDs becoming less deadly in Afghanistan

(CBS News) KABUL - In Afghanistan, seven American troops were killed over the weekend, six of them in one bombing.

It's summer, the peak of the fighting season there. There was another attack in Afghanistan's second largest city, Kandahar.

The six American soldiers killed in one bombing were on patrol in an armored vehicle southwest of Kabul when they struck an enormous roadside bomb.

It's estimated the bomb contained roughly 200 pounds of homemade explosives. Coalition forces are still investigating this attack, but the overall number of fatalities from improvised explosive devices -- or IEDs -- in Afghanistan is actually going down.

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Those roadside bombs used to be the leading cause of deaths for troops in Afghanistan, but their effectiveness has been reduced because of advances in training, equipment and intelligence.

Two years ago, 368 soldiers were killed by IED.s. So far this year, 77 have been killed.

So while these deadly ambushes are still a major threat to soldiers here, the numbers are going down.