Traffic backs up on Airline Highway heading south at Old Perkins Road, La. 427, Wednesday August 1, 2018, in Prairieville. Planners working for Ascension Parish government are working on a new master land use plan that would lay how the parish should grow in the future and plan for infrastruture.

GONZALES — With new I-10 interchanges, wider state highways and commuter bus and park-and-ride options, Ascension Parish's new transportation master plan proposes an ambitious transformation of the parish's road grid over the next 20 years or more.

Unveiled this week in open houses, the plan proposes spending $1.25 billion on parish, state and federal byways between 2023 and 2038 or later and prioritizes the projects in four phases. The plan's projects would come after the parish's current nearly $60 million Move Ascension program, which tackles safety-oriented and smaller-scale traffic flow improvements across the parish, is finished.

The plan is coming out as the parish government also is taking steps to finalize its master plan for the growth, a kind of development blueprint for the next 25 years.

Both are on a track to gain final approval in June, parish officials said. Public open house meetings on the master plan are scheduled at the end of the month.

The first $475 million phase of the transportation plan would include improving traffic flow in existing congested areas, including adding more lanes to I-10, Airline Highway and La. 30 and other improvements and calls for building new or expanded I-10 interchanges at Bluff Road, La. 74 and Cornerview Road.

Later phases emphasize highways and roads that could promote economic development, including a long-discussed connection in western Ascension that would tie La. 3127 to La. 1 and River Road and widening La. 74, La. 73 and La. 931 to from two or three lanes to four lanes.

Kip Strauss, one of the consultants with HNTB who helped develop the plan, said his firm used a specialized prioritization tool, engineering judgment and talks with a parish steering committee to decide how to prioritize projects.

But he said in an interview at an open house Thursday in Gonzales, the point of the open house meetings was to collect public views on the priority plan to spot areas that might have missed or under estimated.

The high-level plan doesn't drill deeply into the details of projects. For instance, the plan calls for a series of intersection upgrades across the parish road grid but leaves to future analysis what those improvements should be, whether roundabouts, new turn lanes with traffic signals or other options, Strauss said.

The plan also doesn't explain how all the work would be paid for but simply underscores a current funding gap of $40 million annually in road spending that would be necessary for more than 20 years to achieve the plan. The plan lays out possible new funding options — new taxes, tolls, bonds or fees.

The plan says the parish needs to find $60 million per year in road spending over the next 20 years to finance all the master plan's concepts but only generates $20 million per year through a combination of state and parish resources.

The parish's dedicated road tax — two-thirds of a half-cent sales tax — road impact fees and other sales tax surplus generate about $7 million per year while the state kicks in another $12 million per year, the plan's presentation materials say. 

Strauss said the $60 million per year in funding that the plan says is necessary matches what past academic research has found counties and parishes of Ascension's population size have been determined to need for adequate transportation systems.

Follow David J. Mitchell on Twitter, @NewsieDave.