David J Plazak

Use of Physical Devices for Calming Traffic Along Major Roads Through Small Rural Communities in Iowa

Many rural communities have developed around highways or major county roads. As a result, the main street through small rural communities is often part of a high-speed rural highway. Highways and county roads are characterized by high speeds outside the city limits and then transition into a reduced-speed section through the rural community. Consequently, drivers passing through the community may enter at high speeds and then maintain those speeds throughout. Traffic calming in small rural communities along major roadways is common in Europe, but the United States does not have experience with applying traffic calming outside of major urban areas. Seven different low-cost traffic treatments were implemented and evaluated in five rural Iowa communities. Two of the treatments physically affected the roadway cross-section. A speed table was placed along the major road (County Highway E-23) in Gilbert, Iowa, and longitudinal channelizers were used to create a center island narrowing along County Highway R-38 in Slater, Iowa. Before and after speed studies were conducted. Speed studies were conducted at 1, 3, 9, and 12 months after installation of the treatments to evaluate their effectiveness over time. Both treatments successfully reduced mean speed, 85th percentile speed, and fraction of vehicles traveling 5, 10, 15, and 20 mph over the posted speed limit; reductions were sustained over time.

APPLICATIONS OF STATE EMPLOYMENT DATA TO TRANSPORTATION PLANNING

A major problem in transportation modeling is the acquisition of quality employment data. Employment data are used in transportation planning to model the journey to work and other types of trips, but they rarely are collected solely for transportation purposes because of the large expense involved. Census data, on the other hand, are inexpensive but are collected only every 10 years (although the American Community Survey provides some continuous data). This presentation outlines and assesses a process to develop systems and protocols for using an already-collected set of detailed employment data for an alternative purpose, transportation planning. Tapping this source may provide an ongoing, economical, and annual source of important transportation data that allows planners to better model and predict transportation needs, from the commuter and the business perspective. A better understanding of travel patterns, in turn, helps planners to evaluate investments in fixed physical infrastructure and public transportation. The data set also has valuable uses in other fields, such as workforce development planning, economic development, land use planning, and social service delivery. The success of this project required intergovernmental cooperation from several key partners.

Dedicated Truck Facilities as Solution to Capacity and Safety Issues on Rural Interstate Highway Corridors

This paper identifies the safety and operational benefits of constructing dedicated truck facilities on a rural Interstate corridor. The Interstate highway segment in the case study is a 164-mi section of I-80 from the Iowa–Illinois border to Altoona, Iowa (an eastern suburb of Des Moines, Iowa). Although many studies have considered constructing an additional lane on freeways and designating it for trucks only, this paper considers the construction of a separate four-lane, limited-access facility for trucks. The I-80 corridor was analyzed with the Highway Economic Requirements Software–state edition (HERS-ST) to measure the performance before and after trucks were removed from the general purpose lanes. Several benefit-to-cost ratios were calculated outside of HERS-ST to determine the economic feasibility (but not the financial feasibility) of constructing dedicated truck lanes. Since there are no similar truck-only facilities in the United States, it is unknown what proportion of motor carriers would choose to use a truck-only facility rather than the mixed-traffic lanes (general purpose lanes), and future policy may or may not require trucks to use parallel truck-only facilities. Therefore, a sensitivity analysis was conducted within the benefit-to-cost analysis to determine the benefits of diverting 100%, 75%, 50%, and 25% of trucks to a dedicated truck facility. At all levels of diversion, the benefits exceed the costs. Although the analysis shows that a truck-only facility is desirable, the policy framework to make such a facility physically and financially feasible does not exist in federal or Iowa policy.

Access Management Plan and Program for Des Moines, Iowa, Metropolitan Area

According to the Iowa Department of Transportations crash database (GIS-ALAS), between 5% and 10% of all crashes in Iowa occur at commercial driveways. Most of these occur at arterials within municipalities. In recent years, nearly one-quarter of these crashes occurred in the Des Moines metropolitan area, making the area a prime candidate for improved access management. Case study research in Iowa has shown that access management is an effective highway safety tool: well-managed routes can be 40% to 50% safer than poorly managed routes. The Des Moines metropolitan area has many miles of older arterials that were constructed before access management was considered. This paper describes a cooperative effort of the Des Moines Area Metropolitan Planning Organization and the Center for Transportation Research and Education at Iowa State University to develop an access management study and program for the Des Moines metro area. The overall goal of the study is to use the knowledge developed to make improvement...

Use of Geospatial Information and Remote Sensing Data to Support Improved Roadway Access Management

Urban and suburban roadways serve two distinct and sometimes conflicting purposes; they provide mobility and allow access to land and land developments. High-level urban roadways (e.g. arterials) should primarily serve mobility needs of travelers and goods. Low level, local roadways should primarily allow for land development access. Arterials that allow too much direct land access fail to function properly in terms of both traffic operations and safety. Such roadways are in need of access management. The operational and safety benefits of access management are impressive. Access management has been shown to reduce crash rates on urban and suburban arterials by up to 40 to 50 percent. Identification of access management problem corridors (or corridors with excellent crash reduction potential) can be done in several ways. Physical features inconsistent with good access management practices can be identified. Alternatively, crash records can be used to identify outbreaks of crash types associated with poor access management. Ideally, both approaches may be used together. This paper highlights four examples from the State of Iowa in the United States of the use of remote sensing imagery to extract access features and crash records to identify corridors with the most promise for improving safety through better access management. All four of these research studies are now being used by the Iowa Department of Transportation and/or metropolitan planning organizations in Iowa to improve the safety and operational performance of their urban arterials and other major roadways. Applications discussed in this paper include using remote sensing for estimating the level of access management, high priority commuting corridor identification the state of Iowa, regional access management planning for the Des Moines, Iowa USA metropolitan area, and the use of remote sensing for land use change detection and traffic monitoring.