With the blustery winter weather behind them, Seattle drivers should be relieved to be driving on ice and snow-free roads.

But not all of the roadway obstacles have been washed away by warmer weather.

Road damage greatly increases after icy and wet weather occurs, according to spokesmen for both Washington state and Seattle departments of transportation.

The most common forms of road damage are potholes and spalling, where the crack between two slabs of concrete in a road warps and deteriorates.

These are generally caused when street pavement becomes fatigued and is subsequently driven over by vehicles; moisture significantly contributes to this fatigue.

"It really has to do with water getting into the structure of roadways, freezing and thawing and that happening repeatedly," said Stan Suchan, spokesman for the Washington State Department of Transportation (WSDOT). "That's why you see more potholes in the winter and spring than in the summer. It's that freeze-thaw process that breaks apart roadways."

Gregg Hirakawa, spokesman for Seattle Department of Transportation (SDOT) said, "I can't tell you that in cold weather we'll see 'x' [more] potholes than in a warm, dry winter. I can tell you that consistent with the weather conditions, we see an increased number of potholes and road damage."

In 2005, a relatively dry year for Seattle standards, 45,812 potholes were filled in Seattle.

The most pothole-filled year recently was 2002, when 106,371 potholes were fixed. Hirakawa said the election of Greg Nickels as mayor had much to do with the attention placed on fixing dented Seattle streets.

"Mayor Nickels was elected in 2001 and he was the one to put forth the 48-hour rule," Hirakawa said. "If you report a pothole to [SDOT], we try to fill it within 48 hours within receiving the report. We have a 94 to 98 percent compliance level."

About 60,000 potholes were filled in 2006 at a cost of roughly $35 per pothole, said Hirakawa; that's an estimated $2.1 million spent fixing potholes alone.

2006 saw wetter weather than rainy Seattle is accustomed to; November brought the city enough rain to break the record rainfall with 15.63 inches of rain, according to the Associated Press.

This breaks the previous record set in December 1933 of 15.33 inches.

November also saw historic temperature lows at Sea-Tac Airport of 18 degrees, which broke the previous record of 22 degrees recorded in November 1985.

In addition to increased rainfall, Washington state was hit with three snow days that blanketed roadways with sleet and ice.

Downtown Seattle and surrounding areas like the U-District caught the lighter end of these storms, while North and South Seattle were overwhelmed with snow.

The total damage costs from recent storms is not yet clear, Hirakawa said, and assessing the damage solely caused by specific spots of bad weather is also difficult.

"It's one of those things that doesn't track too clearly," he said. "We don't get into the causation issue [with road damage], we just fill [the hole]. Certain roads might withstand cold freezing and thawing better than others. A newer road, for example, will probably have a little more tolerance than an older one. I think overall, as we get several months in after the new year, we'll have a better idea."

Even if you pay attention to weather forecasts, it's difficult to prevent dangerous road conditions.

Liquid deicer is typically used before snow hits the ground; the WSDOT employed such a method before November's snowstorm during the Seahawks' game against the Green Bay Packers. Despite the effort, roads were still icy for days afterward.

"There was enough water moving around before the freeze hit that we couldn't keep it down," said Suchan. "There's certainly no anti-ice road deicer that can keep roads bare during wet storms."

The method used after snowfall typically consists of sand mixed with chemical deicing salts, which gradually eats away at frozen roads and provides traction for passing vehicles.

Certain chemicals are avoided because of possible damage to the environment and to vehicles. Since the Thanksgiving Day storm, the SDOT dropped 2,600 tons of sand on city streets. But the more traffic passing over these treated areas, especially on highways, the less effective they become.

"If you put [sand and deicer] down and there's 60-mph traffic on it, it blows away," said Suchan.

With the weather getting warmer by the day, Seattle drivers may not have to worry about icy driving conditions — just look out for that dip in the road.

Reach reporter Tiffany Wan at news@thedaily.washington.edu.