Modernizing Iowa’s highways – what does that really mean?
As part of a series of blog posts about transportation asset management and what that means at the Iowa Department of Transportation, this article focuses on a little Iowa transportation system history and where we go from here.
The Iowa DOT has responsibility for the Primary Highway System that includes state highways (i.e., Iowa 10 in northwest Iowa), U.S. highways (i.e., U.S. 30 across the state), and the interstate system. Cities and counties are responsible to construct and maintain their own systems. As you read in the initial asset management post in November, the Iowa DOT maintains more than 9,400 miles of state-owned highways and ramps and nearly 4,200 bridges. Many of those roads and bridges were built from the 1920s to the 1960s. What many people may not understand is the county road system accounts for another almost 89,000 miles of highways and 19,000 bridges and cities maintain nearly 15,000 miles of road and more than 1,100 bridges. Iowa’s complete roadway network currently ranks fifth in the nation in the total number of bridges and 13th in overall miles of roadways. As a state, we rank 30th in population. This all adds up to a very dense transportation system compared to the size and population of our state.
How has our highway system changed over time?
From a few hundred Model Ts on mud roads to modern semi-tractor trailers hauling huge wind turbine blades down a busy interstate, transportation needs have changed significantly over the years. Initially, the focus was on connecting Iowa’s small and widely dispersed population, which included linking tens of thousands of farms to market towns and cities.
The needs relating to our vast transportation system have changed as Iowa’s population shifts from rural areas to larger cities. Traffic patterns and demands are reflecting that change. The Primary Highway System represents 8.2 percent of the total road mileage in the state. However, these roads carry 61.8 percent of all vehicular traffic.
Over the years, the amount of traffic on Iowa’s roads has significantly increased. As an example, traffic on Interstate 80 just east of Des Moines as increased nearly 24 percent over the last 15 years. In 2000, the recorded traffic level in this area was 60,851 vehicles per day. In 2014, that daily total had climbed to 75,290.
As Iowa looks to achieve further economic growth, the state is taking a critical look at our state highway system and where best to spend resources to not only improve the physical condition of the transportation network, but to also enhance the system’s ability to provide safe, efficient, convenient and reliable mobility.
Time marches on
Because they were constructed many years ago, many of Iowa’s roads and bridges no longer meet current highway design standards. While progress has been made, many roads remain difficult to navigate for today’s larger and heavier freight traffic. This causes these vehicles to travel out of the way to get goods you need from point A to point B. Additional miles on the road means additional cost for the shipper and, eventually you, the consumer.
To address mobility and safety issues, past projects have focused on things such as widening narrow lanes, addressing inadequate bridge heights and widths or dangerously tight curves. Other safety improvements include removing obstacles to allow safe zones and increase the distance drivers are able to see; adding or improving medians; improving lighting; adding rumble strips, widening lanes; widening and paving shoulders; upgrading roads from two lanes to four lanes; improving intersections and pavement markings; and adding traffic signals.
Roadway and bridge improvements benefit customers by cutting down on vehicle maintenance costs, reducing delays and the amount of fuel used, improving safety, reduced road and bridge maintenance costs, and reducing emissions for a cleaner environment.
How much improvement do we need?
The American Association of State Highway and Transportation Officials, a national group made up of state DOTs and other transportation professionals, produces highway specifications for states to follow to help them build roadways are consistent as you travel across the nation. Those specifications include a number of different options that may or may not work for every state. In Iowa, we use those specifications as guidelines to develop our own set of parameters to design roads that further address Iowa’s unique needs.
Deanna Maifield, the Iowa DOT engineer in charge of blending the national standards with Iowa’s project-specific decisions, says that the AASHTO guidelines often include all the “bells and whistles.”
She said, “In Iowa, we don’t always need to include all the improvements suggested by AASHTO to successfully modernize our roads and bridges. Since these standards offer a variety of options to consider, we are looking more critically at what is truly needed versus including every option for each project.”
For Iowa DOT highway designers, there are a few key elements that are in play with every project. Maifield said, “This transportation system belongs to the people who use it. We listen to what our customers want and need, then weigh the cost of the project to the benefit it will provide. We then identify projects to fund where there is a tangible benefit.”
For several years, Iowa has not been able to fully fund all of the roads and bridges in need of repair. This has created a back log of projects. She said, “Our goal now is to complete several good projects to help spread funding further, rather than completing a few great ones.”
In the design process, critical eyes pour over lots and lots of data. Maifield said, “We are fortunate in Iowa that we have a good geographic information system that allows us to collect and analyze a variety of data factors to help make better decisions on which roadways or bridges need to be updated. After that, we’ll look at how we determine which elements to include in those projects.”
Working to keep Iowa’s transportation system safely functioning efficiently and conveniently is at the heart of the work done every day by Iowa DOT highway engineers and designers. Part of our transportation asset management program focuses on making good decisions about the exact elements to be included in each highway or bridge project, backed by data, nationally recognized engineering principles, and a lot of common sense.
In the next blog post, we’ll take a look at how the Iowa DOT rates pavements so we know what roads are most in need of repair.