Evaluation of Different Methods to Calculate Heavy-Truck VMT, Final Report, December 2004

Reliable estimates of heavy-truck volumes are important in a number of transportation applications. Estimates of truck volumes are necessary for pavement design and pavement management. Truck volumes are important in traffic safety. The number of trucks on the road also influences roadway capacity and traffic operations. Additionally, heavy vehicles pollute at higher rates than passenger vehicles. Consequently, reliable estimates of heavy-truck vehicle miles traveled (VMT) are important in creating accurate inventories of on-road emissions. This research evaluated three different methods to calculate heavy-truck annual average daily traffic (AADT) which can subsequently be used to estimate vehicle miles traveled (VMT). Traffic data from continuous count stations provided by the Iowa DOT were used to estimate AADT for two different truck groups (single-unit and multi-unit) using the three methods. The first method developed monthly and daily expansion factors for each truck group. The second and third methods created general expansion factors for all vehicles. Accuracy of the three methods was compared using n-fold cross-validation. In n-fold cross-validation, data are split into n partitions, and data from the nth partition are used to validate the remaining data. A comparison of the accuracy of the three methods was made using the estimates of prediction error obtained from cross-validation. The prediction error was determined by averaging the squared error between the estimated AADT and the actual AADT. Overall, the prediction error was the lowest for the method that developed expansion factors separately for the different truck groups for both single- and multi-unit trucks. This indicates that use of expansion factors specific to heavy trucks results in better estimates of AADT, and, subsequently, VMT, than using aggregate expansion factors and applying a percentage of trucks. Monthly, daily, and weekly traffic patterns were also evaluated. Significant variation exists in the temporal and seasonal patterns of heavy trucks as compared to passenger vehicles. This suggests that the use of aggregate expansion factors fails to adequately describe truck travel patterns.

Evaluation of the Iowa Department of Transportation's Compensatory Wetland Mitgation Program, August 30, 2004

The purpose of this investigation was to evaluate the Compensatory Wetland Mitigation Program at the Iowa Department of Transportation (DOT) in terms of regulatory compliance. Specific objectives included: 1) Determining if study sites meet the definition of a jurisdictional wetland. 2) Determining the degree of compliance with requirements specified in Clean Water Act Section 404 permits. A total of 24 study sites, in four age classes were randomly selected from over 80 sites currently managed by the Iowa DOT. Wetland boundaries were delineated in the field and mitigation compliance was determined by comparing the delineated wetland acreage at each study site to the total wetland acreage requirements specified in individual CWA Section 404 permits. Of the 24 sites evaluated in this study, 58 percent meet or exceed Section 404 permit requirements. Net gain ranged from 0.19 acre to 27.2 acres. Net loss ranged from 0.2 acre to 14.6 acres. The Denver Bypass 1 site was the worst performer, with zero acres of wetland present on the site and the Akron Wetland Mitigation Site was the best performer with slightly more than 27 acres over the permit requirement. Five of the 10 under-performing sites are more than five years post construction, two are five years post construction, one is three years post construction and the remaining two are one year post construction. Of the sites that meet or exceed permit requirements, approximately 93 percent are five years or less post construction and approximately 43 percent are only one year old. Only one of the 14 successful sites is more than five years old. Using Section 404 permit acreage requirements as the criteria for measuring success, 58 percent of the wetland mitigation sites investigated as part of this study are successful. Using net gain/loss as the measure of success, the Compensatory Wetland Mitigation Program has been successful in creating/restoring nearly 44 acres of wetland over what was required by permits.

Synthesis of Best Practice for Increasing Protection and Visibility of Highway Maintenance Vehicles, CTRE Final Report Iowa DOT Project TR-475, August 2002

The purpose of this research project is to study current practices in enhancing visibility and protection of highway maintenance vehicles involved in moving operations such as snow removal and shoulder operations, crack sealing, and pothole patching. The results will enable the maintenance staff to adequately assess the applicability and impact of each strategy to their use and budget. The report’s literature review chapter examines the use of maintenance vehicle warning lights, retroreflective tapes, shadow vehicles and truck-mounted attenuators, and advanced vehicle control systems, as well as other practices to improve visibility for both snowplow operators and vehicles. The chapter concludes that the Manual on Uniform Traffic Control Devices does not specify what color or kind of warning lights to use. Thus, a wide variety of lights are being used on maintenance vehicles. The study of the relevant literatures also suggests that there are no clear guidelines for moving work zones at this time. Two types of surveys were conducted to determine current practices to improve visibility and safety in moving work zones across the country and in the state of Iowa. In the first survey of state departments of transportation, most indicated using amber warning lights on their maintenance vehicles. Almost all the responding states indicated using some form of reflective material on their vehicles to make them more visible. Most participating states indicated that the color of their vehicles is orange. Most states indicated using more warning lights on snow removal vehicles than their other maintenance vehicles. All responding state agencies indicated using shadow vehicles and/or truck-mounted attenuators during their moving operations. In the second survey of Iowa counties, most indicated using very similar traffic control and warning devices during their granular road maintenance and snow removal operations. Mounting warning signs and rotating or strobe lights on the rear of maintenance vehicles is common for Iowa counties. The most common warning devices used during the counties’ snow removal operations are reflective tapes, warning flags, strobe lights, and auxiliary headlamps.

Angle Parking on Iowa's Low Volume Primary Extentions in Small Towns, January 2003

On-street parking has been considered problematic by engineers for many years. In fact, numerous studies have concluded that diagonal or angle parking in particular is potentially more of a safety concern than parallel or no parking at all. It is a common position of many states, including Iowa, to discourage or completely prohibit angle parking on primary road extensions in urban areas. However, with the acceptance of “context sensitive design” and traffic calming techniques, policies for on-street parking are receiving re -consideration in many agencies including the FHWA. This study was undertaken to analyze operational and safety histories in the state of Iowa where various types of on-street parking have existed for many years, concentrating in particular on smaller communities. Specifically of interest was a comparison of diagonal parking locations to other types with regard to related crash histories. If possible, it was intended to develop guidelines to assist Iowa Department of Transportation designers in the consideration of parking requirements for road improvements through small communities. In this regard, several criteria were analyzed to determine possible contribution to crash history including road width, clearance to parked vehicles, traffic volumes, community population, and length of parking area. None of these factors, with the possible exception of population, displayed a clearly definable relationship to crash history. However, when average crash rates for various parking types were compared for non-intersection crashes, differences in rates between areas with diagonal parking and those with parallel parking were almost negligible. In fact, those observed rates were less than sample locations with no parking at all. These results seem to indicate that indeed there may exist no compelling justification for blanket prohibition of angle parking along Iowa’s primary extensions in all urban areas. Rather, a case-by-case investigation with each project design of the most applicable parking type would seem appropriate in smaller communities.

Report of Recommendations to the Iowa Department of Transportation, June 30, 2004

State Audit Reports

Report of Recommendations to the Iowa Department of Public Safety, June 30, 2004

State Audit Reports

An Investigation of User Costs and Benefits of Winter Road Closures, June 2005

This project explores the user costs and benefits of winter road closures. Severe winter weather makes travel unsafe and dramatically increases crash rates. When conditions become unsafe due to winter weather, road closures should allow users to avoid crash costs and eliminate costs associated with rescuing stranded motorists. Therefore, the benefits of road closures are the avoided safety costs. The costs of road closures are the delays that are imposed on motorists and motor carriers who would have made the trip had the road not been closed. This project investigated the costs and benefits of road closures and found that evaluating the benefits and costs is not as simple as it appears. To better understand the costs and benefits of road closures, the project investigates the literature, conducts interviews with shippers and motor carriers, and conducts case studies of road closures to determine what actually occurred on roadways during closures. The project also estimates a statistical model that relates weather severity to crash rates. Although, the statistical model is intended to illustrate the possibility to quantitatively relate measurable and predictable weather conditions to the safety performance of a roadway. In the future, weather conditions such as snow fall intensity, visibility, etc., can be used to make objective measures of the safety performance of a roadway rather than relying on subjective evaluations of field staff. The review of the literature and the interviews clearly illustrate that not all delays (increased travel time) are valued the same. Expected delays (routine delays) are valued at the generalized costs (value of the driver’s time, fuel, insurance, wear and tear on the vehicle, etc.), but unexpected delays are valued much higher because they result in interruption of synchronous activities at the trip’s destination. To reduce the costs of delays resulting from road closures, public agencies should communicate as early as possible the likelihood of a road closure.

Guidelines for the Conversion of Urban Four-Lane Undivided Roadways to Three-Lane Two-Way Left-turn Lane Facilities, April 2001

Four-lane undivided roadways in urban areas can experience a degradation of service and/or safety as traffic volumes increase. In fact, the existence of turning vehicles on this type of roadway has a dramatic effect on both of these factors. The solution identified for these problems is typically the addition of a raised median or two-way left-turn lane (TWLTL). The mobility and safety benefits of these actions have been proven and are discussed in the “Past Research” chapter of this report along with some general cross section selection guidelines. The cost and right-of-way impacts of these actions are widely accepted. These guidelines focus on the evaluation and analysis of an alternative to the typical four-lane undivided cross section improvement approach described above. It has been found that the conversion of a four-lane undivided cross section to three lanes (i.e., one lane in each direction and a TWLTL) can improve safety and maintain an acceptable level of service. These guidelines summarize the results of past research in this area (which is almost nonexistent) and qualitative/quantitative before-and-after safety and operational impacts of case study conversions located throughout the United States and Iowa. Past research confirms that this type of conversion is acceptable or feasible in some situations but for the most part fails to specifically identify those situations. In general, the reviewed case study conversions resulted in a reduction of average or 85th percentile speeds (typically less than five miles per hour) and a relatively dramatic reduction in excessive speeding (a 60 to 70 percent reduction in the number of vehicles traveling five miles per hour faster than the posted speed limit was measured in two cases) and total crashes (reductions between 17 to 62 percent were measured). The 13 roadway conversions considered had average daily traffic volumes of 8,400 to 14,000 vehicles per day (vpd) in Iowa and 9,200 to 24,000 vehicles per day elsewhere. In addition to past research and case study results, a simulation sensitivity analysis was completed to investigate and/or confirm the operational impacts of a four-lane undivided to three-lane conversion. First, the advantages and disadvantages of different corridor simulation packages were identified for this type of analysis. Then, the CORridor SIMulation (CORSIM) software was used x to investigate and evaluate several characteristics related to the operational feasibility of a four-lane undivided to three-lane conversion. Simulated speed and level of service results for both cross sections were documented for different total peak-hour traffic, access densities, and access-point left-turn volumes (for a case study corridor defined by the researchers). These analyses assisted with the identification of the considerations for the operational feasibility determination of a four -lane to three-lane conversion. The results of the simulation analyses primarily confirmed the case study impacts. The CORSIM results indicated only a slight decrease in average arterial speed for through vehicles can be expected for a large range of peak-hour volumes, access densities, and access-point left-turn volumes (given the assumptions and design of the corridor case study evaluated). Typically, the reduction in the simulated average arterial speed (which includes both segment and signal delay) was between zero and four miles per hour when a roadway was converted from a four-lane undivided to a three-lane cross section. The simulated arterial level of service for a converted roadway, however, showed a decrease when the bi-directional peak-hour volume was about 1,750 vehicles per hour (or 17,500 vehicles per day if 10 percent of the daily volume is assumed to occur in the peak hour). Past research by others, however, indicates that 12,000 vehicles per day may be the operational capacity (i.e., level of service E) of a three-lane roadway due to vehicle platooning. The simulation results, along with past research and case study results, appear to support following volume-related feasibility suggestions for four-lane undivided to three-lane cross section conversions. It is recommended that a four-lane undivided to three-lane conversion be considered as a feasible (with respect to volume only) option when bi-directional peak-hour volumes are less than 1,500 vehicles per hour, but that some caution begin to be exercised when the roadway has a bi-directional peak-hour volume between 1,500 and 1,750 vehicles per hour. At and above 1,750 vehicles per hour, the simulation indicated a reduction in arterial level of service. Therefore, at least in Iowa, the feasibility of a four-lane undivided to three-lane conversion should be questioned and/or considered much more closely when a roadway has (or is expected to have) a peak-hour volume of more than 1,750 vehicles. Assuming that 10 percent of the daily traffic occurs during the peak-hour, these volume recommendations would correspond to 15,000 and 17,500 vehicles per day, respectively. These suggestions, however, are based on the results from one idealized case xi study corridor analysis. Individual operational analysis and/or simulations should be completed in detail once a four-lane undivided to three-lane cross section conversion is considered feasible (based on the general suggestions above) for a particular corridor. All of the simulations completed as part of this project also incorporated the optimization of signal timing to minimize vehicle delay along the corridor. A number of determination feasibility factors were identified from a review of the past research, before-and-after case study results, and the simulation sensitivity analysis. The existing and expected (i.e., design period) statuses of these factors are described and should be considered. The characteristics of these factors should be compared to each other, the impacts of other potentially feasible cross section improvements, and the goals/objectives of the community. The factors discussed in these guidelines include • roadway function and environment • overall traffic volume and level of service • turning volumes and patterns • frequent-stop and slow-moving vehicles • weaving, speed, and queues • crash type and patterns • pedestrian and bike activity • right-of-way availability, cost, and acquisition impacts • general characteristics, including - parallel roadways - offset minor street intersections - parallel parking - corner radii - at-grade railroad crossings xii The characteristics of these factors are documented in these guidelines, and their relationship to four-lane undivided to three-lane cross section conversion feasibility identified. This information is summarized along with some evaluative questions in this executive summary and Appendix C. In summary, the results of past research, numerous case studies, and the simulation analyses done as part of this project support the conclusion that in certain circumstances a four-lane undivided to three-lane conversion can be a feasible alternative for the mitigation of operational and/or safety concerns. This feasibility, however, must be determined by an evaluation of the factors identified in these guidelines (along with any others that may be relevant for a individual corridor). The expected benefits, costs, and overall impacts of a four-lane undivided to three-lane conversion should then be compared to the impacts of other feasible alternatives (e.g., adding a raised median) at a particular location.

Two-Lift Portland Cement Concrete Pavements to Meet Public Needs, September 2004

The report reviews the past work in the United States and internationally in the development of two-lift pavements. It points out the strengths and limitations in the construction of such portland cement concrete pavements. Certain cost, mix design, and construction problems are inhibiting the growth of this product. Changes in the availability of aggregates, knowledge of materials and new construction equipment, and the desire for specific surfaces to meet noise, durability, and safety are prompting the need to reconsider this type of construction.

2006-2010 Iowa Transportation Improvement Program

This document provides the planned investments in Iowa's transportation system for the five-year period of 2006-2010. It encompasses aviation, railroads, rivers, trails, state parks and institutional roads, roadways, and public transit.

How Much “Safety��� Is Available under the U.S. Proposal to the WTO?, November 2005

Critics of the U.S. proposal to the World Trade Organization (WTO) made in October 2005 are correct when they argue that adoption of the proposal would significantly reduce available support under the current farm program structure. Using historical prices and yields from 1980 to 2004, we estimate that loan rates would have to drop by 9 percent and target prices would have to drop by 10 percent in order to meet the proposed aggregate Amber Box and Blue Box limits. While this finding should cheer those who think that reform of U.S. farm programs is long overdue, it alarms those who want to maintain a strong safety net for U.S. agriculture. The dilemma of needing to reform farm programs while maintaining a strong safety net could be resolved by redesigning programs so that they target revenue rather than price. Building on a base of 70 percent Green Box income insurance, a program that provides a crop-specific revenue guarantee equal to 98 percent of the product of the current effective target price and expected county yield would fit into the proposed aggregate Amber and Blue Box limits. Payments would be triggered whenever the product of the season-average price and county average yield fell below this 98 percent revenue guarantee. Adding the proposed crop-specific constraints lowers the coverage level to 95 percent. Moving from programs that target price to ones that target revenue would eliminate the rationale for ad hoc disaster payments. Program payments would automatically arrive whenever significant crop losses or economic losses caused by low prices occurred. Also, much of the need for the complicated mechanism (the Standard Reinsurance Agreement) that transfers most risk of the U.S. crop insurance to the federal government would be eliminated because the federal government would directly assume the risk through farm programs. Changing the focus of federal farm programs from price targeting to revenue targeting would not be easy. Farmers have long relied on price supports and the knowledge that crop losses are often adequately covered by heavily subsidized crop insurance or by ad hoc disaster payments. Farmers and their leaders would only be willing to support a change to revenue targeting if they see that the current system is untenable in an era of tight federal budgets and WTO limits.

Iowa Department of Transportation Office of Contracts Letting Summary - July 1, 2004 through June 30, 2005

A summary of the regularly scheduled lettings and emergency/special lettings held by the Iowa Department of Transportation for construction and maintenance work during the period July 1, 2004, through June 30, 2005.

A Review of the Driver's License Issuance Program Administered by the Department of Transportation and the County Treasures, For the Fiscal Year Ended June 30, 2005

Other Audit Reports

Iowa Department of Public Safety Performance Report, FY 2004

Agency Performance Report

Iowa Department of Transportation Performance Report, FY 2004

Agency Performance Report