As directed by Iowa Code Chapter 312, the Treasurer of State distributes money from the state's Road Use Tax Fund to Iowa cities and counties. Street construction and secondary road payments are deposited on the third Tuesday of each month. Transfer of jurisdiction/Farm-to-market extension payments are deposited on the third Friday of each month. Payment dates and amounts are available here.
May 2015 payment is less than usual due to the transfer of annual motor vehicle registrations in excess of $392,000,000 from the Road Use Tax Fund to the TIME-21 Fund per Iowa Code 312.2(17)(a).