Maintenance crews are preparing to pour prevention into plugging a persistent problem on some of the city’s major city streets in the coming year.

Several busy roadways — including Sixth, Iowa, Massachusetts and other streets throughout the community — will be having their pavement cracks filled with liquid tar this summer, part of an ongoing program to preclude potholes from forming.

Officials say the crack-filling work that began just three years ago already is paying off, with fewer stretches of road becoming riddled with the wheel-eating, suspension-knocking and alignment-wrenching craters that give residents plenty of reason to complain about their roads.

“Crack sealing is money well spent,” said Chuck Soules, the city’s director of public works.

Among streets on the list for such work this coming year:

• Sixth Street, from the South Lawrence Trafficway to downtown Lawrence.

• Iowa Street, from Sixth to the southern edge of town.

• Clinton Parkway, from Iowa to Wakarusa Drive.

• Wakarusa, from the trafficway to Bob Billings Parkway.

• Massachusetts Street, from Sixth to 23rd streets, plus all other streets in downtown Lawrence.

• North Second and North Third streets in North Lawrence, from the Union Pacific Railroad bridge to the northern edge of town.

The work is a key part of the city’s maintenance program, because sealing cracks limits the amount of moisture that can seep underneath pavement and into a road’s subsurface, said Mark Thiel, assistant director of public works.

If potholes have a recipe, moisture is the main ingredient.

When water freezes beneath a layer of pavement, the road surface heaves upward, Thiel said. When the pavement gets pushed back down — under the weight of passing trucks and cars — the resulting cracks allow more water to seep in the next time.

The cycle continues until the loosening surface is dislodged, either by passing cars or snowplows.

“If we can keep the moisture from getting down in the pavement, we can prevent, literally, all potholes,” Thiel said. “The caveat out there is we’ll always have potholes … but we can be more effective with the tools that we use to eliminate a larger portion of those.”

Filling cracks with liquid tar — which hardens into a flexible, rubber-like seal within 20 minutes of pouring — costs about 40 cents per square yard of pavement treated, Thiel said. Filling potholes costs about $30 to $40 per square yard.

Roads riddled with potholes can cost hundreds of thousands of dollars to resurface, while rebuilding entire sections can cost millions. The city, for example, is preparing to rebuild Kasold Drive from Clinton Parkway to 31st Street, for an estimated $6.5 million.