Close to the curbs, many residential streets are developing “alligator cracking” - places where the asphalt is sunken and webbed with fissures.

Because they are often in the field, street crews were able to quickly pinpoint what they think the cause might be: a change in Allied Waste''s trash pick-up procedures.

In the past, workers would hop off the trucks and toss bags of trash into the hopper. Trucks tended to rumble down the center of the city''s streets - where the asphalt is thicker and stronger.

But with so many households using blue carts, workers now use mechanical arms to lift the carts. To reach them, the trash trucks drive close to the curb, where the asphalt is weaker.

Most of the deteriorating residential streets are located on the East Side and the South Side. But streets near Belair Elementary School and McKay Park also have some problems, as do those west of Southwest Boulevard.

Over time, not all streets were built to the same standards. Some are more poorly constructed than others.