Revision to the SUDAS Traffic Signal Standards – Phase 2, Final Report, May 2012

This report provides a summary of the updates to the traffic signal content within the Iowa Statewide Urban Design and Specifications (SUDAS) Design Manual Chapter 13 and Standard Specifications Division 8. Major focal points included pole footing design, cabinets and controllers, monitoring systems, communications systems, and figure updates. This work was completed through a project task force with a variety of participants (contractors, Iowa Department of Transportation, city traffic engineers, consultant, vendors, and University research and support staff).

Age vs. Experience: Evaluation of a Video Feedback Intervention for Newly Licensed Teen Drivers, TPF-5(207), 2013

This project examines the effects of age, experience, and video-based feedback on the rate and type of safety-relevant events captured on video event recorders in the vehicles of three groups of newly licensed young drivers: 1. 14.5- to 15.5-year-old drivers who hold a minor school license (see Appendix A for the provisions of the Iowa code governing minor school licenses); 2. 16-year-old drivers with an intermediate license who are driving unsupervised for the first time; 3. 16-year-old drivers with an intermediate license who previously drove unsupervised for at least four months with a school license. METHODS: The young drivers’ vehicles were equipped with an event-triggered video recording device for 24 weeks. Half of the participants received feedback regarding their driving, and the other half received no feedback at all and served as a control group. The number of safety-relevant events per 1,000 miles (i.e., “event rate”) was analyzed for 90 participants who completed the study. RESULTS: On average, the young drivers who received the video-based intervention had significantly lower event rates than those in the control group. This finding was true for all three groups. An effect of experience was seen for drivers in the control group; the 16-year-olds with driving experience had significantly lower event rates than the 16-year-olds without experience. When the intervention concluded, an increase in event rate was seen for the school license holders, but not for either group of 16-year-old drivers. There is strong evidence that giving young drivers video-based feedback, regardless of their age or level of driving experience, is effective in reducing the rate of safety-relevant events relative to a control group who do not receive feedback. Specific comparisons with regard to age and experience indicated that the age of the driver did not have an effect on the rate of safety-events, while experience did. Young drivers with six months or more of additional experience behind the wheel had nearly half as many safety-relevant events as those without that experience.

Dynamic Speed Feedback Signs, 2014

Dynamic speed feedback sign (DSFS) systems are traffic control devices that are programmed to provide a message to drivers exceeding a certain speed thresh¬old. A DSFS system typically consists of a speed-measuring device, which may be loop detectors or radar, and a message sign that displays feedback to drivers who exceed a predetermined speed threshold. The feedback may be the driver’s actual speed, a message like “SLOW DOWN,” or activation of a warning device such as beacons or a curve warning sign. For more on this topic by these authors, see also "Evaluation of Dynamic Speed Feedback Signs on Curves: A National Demonstration Project": http://www.trb.org/main/blurbs/172092.aspx

Revision to the SUDAS Traffic Signal Design Guide, TR-546, 2009

Changes in technology have an impact on standard practice, materials, and equipment. The traffic signal industry is constantly producing more energy-efficient and durable equipment, better communications, and more sophisticated detection and monitoring capabilities. Accordingly, this project provides an update to the traffic signal content within the Statewide Urban Design and Specifications (SUDAS) Design Manual and Standard Specifications. This work was completed through a technical advisory committee with a variety of participants representing contractors, the Iowa Department of Transportation, cities, consultants, vendors, and university research and support staff.

Improved Methods for Determining Wind Loads on Highway Sign and Traffic-Signal Structures, TR-559, 2007

The main objective of the proposed study is to use Computational Fluid Dynamics (CFD) tools to determine the wind loads by accurate numerical simulations of air flow characteristics around large highway sign structures under severe wind speeds conditions. Fully three-dimensional Reynolds- Averaged Navier-Stokes (RANS) simulations are used to estimate the total force on different panels, as well as the actual pressure distribution on the front and back faces of the panels. In particular, the present study investigates the effects of aspect ratio and sign spacing for regular panels, the effect of sign depth for the dynamic message signs that are now being used on Iowa highways, the effect induced by the presence of back-to-back signs, the effect of the presence of add-on exit signs, and the effect of the presence of trucks underneath the signs potentially creating “wind tunnel” effect.

Revision to the SUDAS Traffic Signal Standards - Phase 2, 2012

This report provides a summary of the updates to the traffic signal content within the Iowa Statewide Urban Design and Specifications (SUDAS) Design Manual Chapter 13 and Standard Specifications Division 8. Major focal points included pole footing design, cabinets and controllers, monitoring systems, communications systems, and figure updates. This work was completed through a project task force with a variety of participants (contractors, Iowa Department of Transportation, city traffic engineers, consultant, vendors, and University research and support staff).

Traffic Signal Inventory Project, 2001

The Center for Transportation Research and Education performed a traffic signal inventory study for the Iowa Department of Transportation. The purpose of this study was to determine the level of compliance with the Manual on Uniform Traffic Control Devices (MUTCD) and other industry standards of traffic signals on the state highway system. Signals were randomly selected throughout the State of Iowa. Only signals in cities with a population less than 5,000 were considered. Several intersections need to be addressed immediately to correct clearance timing settings. Red clearance intervals were frequently too short. A handful of intersections had inadequate pedestrian clearance times. Six intersections had at least one yellow clearance interval that did not meet Institute of Transportation Engineers standards. Some of the intersections likely would not meet traffic signal warrants and should be investigated for possible removal. The most common problem found with traffic signals was a lack of maintenance. Many of the signals had at least one of the following problems: burned out lights (signals and/or pedestrian heads), pedestrian lenses in need of replacement, dirty cabinet/missing or poor filter, missing visors, or inoperative pedestrian push buttons. Timing sheets were frequently missing or out of date. Another frequent noncompliance issue was the use of backplates. The MUTCD states that backplates should be used on signals viewed against a bright sky. The majority of signals inventoried did not have backplates on the mast-arm mounted signals. The timing at some intersections could likely be improved by reducing the cycle length. Where there were multiple signals in close proximity rarely was there any attempt at signal coordination. Finally, a number of intersections had equipment that by today’s standards would be considered obsolete.