Crunching road dollars: An Ada County Highway District analysis of $814 million spent on road projects from 2001 to 2012 shows that each of the county’s six cities roughly gets back in services what it pays into the system, although some inequities do occur.

Why the inequities? Fast-growing cities in western Ada County have been getting a slightly larger share of recent roadway spending because ACHD must build new roads or expand existing ones to accommodate residential or commercial development. Additionally, some imbalance can occur in any given year or if one city has a particularly large project, according to the study.

Big projects: Meridian’s $18 million split-corridor project and Boise’s $21 million East ParkCenter Bridge skewed the numbers in each city’s favor in the years they were constructed.

The trend line is about to bend: Boise, which has slightly more than half of the county’s population, stands to get $6 of every $10 ACHD spends on construction through 2020, the analysis shows. One reason: The 30th Street extension, a project that broke ground on Wednesday and is scheduled to be completed in October. The new $9.1 million road will connect State Street to Fairview Avenue. Changes also are planned along State Street over the next few years.