City maintenance leaders have started coating more of Oahu’s roads with sealants that are commonly used elsewhere to preserve streets — but they’ve still got a long way to go to cover the entire island.

Honolulu Mayor Kirk Caldwell’s office announced this week that the city plans to treat 43 lane miles of mostly residential roadway in Pearl City with seal coat. That’s part of the 63 total lane miles the city plans to coat with the substance this year, according to maintenance officials.

Local paving company Alakona Corp. has a $2.6 million contract to treat the more than 90 Pearl City streets with seal coat through December, according to a news release.

This is the first year that the city plans to use seal coat on a widespread basis. In 2015 the city started treatments by applying the emulsion material to 2 lane miles of road, according to Department of Facility Maintenance Director Ross Sasamura.

Along with slurry seal, seal coat is one of several materials that asphalt industry experts say are key to help extend the life and improve the quality of a region’s road network. Such road preservation treatments have been around for decades, although Honolulu has only recently started using them and only on a small fraction of the island’s roadways so far.

Since 2010 the city has coated some 164 lane miles of road with slurry seal, according to Sasamura. It’s also treated more than 220,000 feet of cracks in the road asphalt with sealant materials since 2015, according to Sasamura.

The city maintains about 3,500 total lane miles of road across Oahu. That doesn’t include highways such as H-1, Nimitz and Kamehameha, which the state maintains.

DFM staff continues to study which city streets across Oahu have the right traffic loads and pavement conditions to be treated with seal coat and other preservation materials, Sasamura said in an email Wednesday. Seal coat works better on low-traffic streets, and if the roads are too damaged, then applying preservation materials won’t do any good, officials have said.

Seal coat treatments could extend the life of a street that’s deemed appropriate for them by five to seven years in between resurfacing work, according to Sasamura.

Caldwell has touted the record number of lane miles across the island that the city has repaved since he took office in 2013. However, city maintenance officials are still developing a comprehensive, islandwide pavement preservation program to help keep city roads smoother after they’re repaved.

“The need to apply pavement preservation products remain as a vital step in prolonging the life of our city streets,” Sasamura wrote Wednesday.

The seal-coat work in Pearl City will start June 6, with work being done from 8:30 a.m. to 3:30 p.m., according to a city news release. Residents and businesses there will be notified before work starts, the release said.