TAC Transportation Intelligence

Planning (voir aussi Planification)

Measurement and Evaluation of Transit Travel Time Reliability
Transit travel time reliability often continues to be viewed by transit agencies solely on the basis of overall on-time performance. Therefore, this research sought to increase knowledge about the causes of travel time variability in transit by comparing the on-time performance and runtime deviation of routes and portions of routes based on specific characteristics of the service (right-of-way, stop spacing, load factors, etc.). Three questions were addressed: (1) What are the characteristics of route segments where travel times (as measured by runtime) are the least variable? (2) What are the characteristics of route segments where drivers are least likely to fall behind? (3) What are the characteristics of route segments where drivers are most likely to be able to catch-up if they have fallen behind schedule? (University of Washington Transportation Northwest Regional Center report TNW2010-10, January 2011, 22p.)

Getting Around When You're Just Getting By: The Travel Behavior and Transportation Expenditures of Low-Income Adults
How much do people with limited resources pay for cars, public transit, and other means of travel? How does their transportation behavior change during periods of falling employment and rising fuel prices? This research uses in-depth interviews with 73 adults to examine how rising transportation costs impact low-income families. The interviews examine four general areas of interest: travel behavior and transportation spending patterns; the costs and benefits of alternative modes of travel; cost management strategies; and opinions about the effect of changing transportation prices on travel behavior. (San José State University. Mineta Transportation Institute report, June 2011, 126p.)

State Traffic Information Systems Improvements: Promising Practices
This report highlights the major State-level accomplishments since 2005 in improving data systems used in traffic safety decision making. A nationwide assessment of traffic records system improvements solicited information from all NHTSA regions and all States plus the District of Columbia and U.S. territories. States were asked to report data quality improvement efforts taking place during the years following passage of the Safe Accountable Flexible Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) in 2005. The project was designed to identify improvements in crash, roadway, driver, vehicle, citation/adjudication, and injury surveillance datasets—the six major components of State traffic records systems. Improvements were sought in the data quality attributes of timeliness, accuracy, completeness, consistency, integration, and accessibility. State projects with quantitative measures showing data quality improvement are highlighted. Additional projects with qualitative evidence of data quality improvement are also described. Several States are listed as pursuing promising practices and the most effective of these are recommended for promotion to the traffic safety and traffic records community. (US National Highway Traffic Safety Administration report, July 2011, 100p.)

Enhancing Internal Trip Capture Estimation for Mixed-Use Developments
This report provides an improved methodology to estimate how many internal trips will be generated in mixed-use developments—trips for which both the origin and destination are within the development. The methodology estimates morning and afternoon peak–period trips to and from six specific land use categories: office, retail, restaurant, residential, cinema, and hotel. The research team analyzed existing data from prior surveys and collected new data at three mixed-use development sites. The resulting methodology is incorporated into a spreadsheet model, which can be downloaded from the TRB website at http://www.trb.org/Main/Blurbs/165014.aspx. This report will be valuable to transportation agency planners and developers who need to provide or fund facilities that meet the transportation demand generated by new developments. (TRB's National Cooperative Highway Research Program (NCHRP) report 684, 2011, 163p.)

Travel Behavior of the Lone Rangers: An Application of Attitudinal Structural Equation Modeling to Intercity Transportation Market Segmentation
Travel behavior information is valuable to transportation policymakers, planners, and service providers. While aggregate data is helpful, segmenting a market into smaller groups allows for more targeted planning, promotion, operation, and evaluation. In this study, intercity market segments based on traveler attitudes are identified using structural equation modeling (SEM). The study focuses on rural and small urban areas, using survey data for residents of North Dakota and west central and northwest Minnesota. Attitudes toward travel time, flexibility, and privacy are found to have the strongest explanatory power. (North Dakota State University. Upper Great Plains Transportation Institute report, April 2011, 29p.)

Enabling Cost-Effective Multimodal Trip Planners through Open Transit Data
This study examined whether multimodal trip planners can be developed using open-source software and open data sources. OpenStreetMap (OSM), maintained by the non-profit OpenStreetMap Foundation, is an open, freely available international repository of geographic data that individuals contribute about their communities. In the transit industry, Google’s offer of a free online transit trip planner based on the General Transit Feed Specification (GTFS) has made GTFS a de facto standard for describing transit systems and a platform for many other Web and mobile applications. Bus stop locations can link OSM and GTFS data. OpenTripPlanner is an open-source multimodal trip planning software system with an active developer community. The study team set up an instance of OpenTripPlanner for Tampa, Florida, using biking and walking data from OSM, and GTFS data from local transit agencies, to examine the tool’s ability to route using multimodal data. (University of South Florida National Center for Transit Research Report USF 21177926, May 2011, 115p.)

Pavements (voir aussi Chaussées)

A Study on Warm-Mix Asphalt
The Illinois Department of Transportation (IDOT) had an immediate need to evaluate the performance characteristics of new asphalt mixtures. The new mixtures included warm mix asphalt (WMA), stone-matrix asphalt (SMA) with recycled asphalt shingles (RAS), and asphalt mixtures containing alternate friction aggregates (diabase, quartzite, and granite). The object of this project was to compare these new mixes and to provide IDOT with guidance on the applicability of the mix designs when implementing these mixtures in the future. (Illinois Center for Transportation report FHWA-ICT-11-085, June 2011, 78p.)

Development of Methods to Control Cold Temperature and Fatigue Cracking for Asphalt Mixtures
Pavement distresses caused by low and intermediate temperatures are a significant source of problems for highway agencies. While many tests have been developed to address this type of distress, few of them are considered practical for day to day operations. This report presents a methodology for controlling low temperature properties of asphalt mixtures by using the Bending Beam Rheometer (BBR). Through a rigorous statistical analysis, the number of replicate samples needed for valid conclusions was determined so that the test can be used for quality control/quality assurance during asphalt construction. (Utah Department of Transportation report UT-10.08, May 2011, 116p.)

Evaluation of Various Hot Mix Asphalt Pavement Thicknesses Over Rubblized Concrete Pavement
In 1999, the Wisconsin DOT constructed two test sections as part of a rubblized PCC pavement project on I-39 to evaluate whether increased HMA thickness could extend the pavement system's service life. Design thicknesses of the control and test sections 1 and 2 were 6.75, 8.5 and 10.25 inches, respectively. On average, a 1.0-in increase in HMA thickness resulted in a 3x10(^-6) strain reduction. The highest strain that occurred at the 9.5-kip load level, calculated in the control section with a pavement temperature of 71°F, was 56x10"6. This strain level is lower than the commonly accepted endurance limit range of 70x 10(^-6) to 100x10(^-6), indicating that even the thinnest pavement section would provide adequate fatigue protection. A series of LCCAs showed that an unrealistic extension of service life would be required for additional HMA thickness to be cost-effective. Although distress formation was delayed and a small strain reduction resulted from increased HMA thickness in the test sections, these relatively small gains do not justify the increase in construction and material costs. The study results suggest that additional HMA thickness is not necessary for long-term performance and is likely not a cost-effective method of extending a rubblized pavement system's service life. (Wisconsin Department of Transportation report FEP-07-10, July 2010, 47p.)

Traffic Control (voir aussi Gestion de la circulation)

Pedestrian and Bicyclist Traffic Control Device Evaluation Methods
The purpose of this primer is to introduce and define the active traffic management (ATM) and TDM concepts and show the need for and benefits of integrating the concepts into efforts to address congestion on the most affected facilities. The primer provides a conceptual framework, originally suggested by the Dutch Ministry of Transport, for understanding the difference between traffic management and travel demand management. The primer underscores the need to integrate the two concepts into a holistic approach to congestion management. Considered alone, each concept presented in this primer is neither new nor innovative. What is new and innovative is the call to consider an integrated approach from the earliest planning stages of efforts to address congestion in a given region, system, or corridor. (US Federal Highway Administration report FHWA-HRT-11-035, May 2011, 96p.)

Development of Mobile Accessible Pedestrian Signals (MAPS) for Blind Pedestrians at Signalized Intersections
Among the intersection crossing sub-tasks, locating crosswalk, determining when to cross and maintaining alignment to crosswalk while crossing are the most difficult tasks for the blind and visually impaired. To understand how the blind pedestrians make safe crossing decisions, ten blind and low-vision individuals were interviewed. to understand the types of information they use while making safe intersection crossings and identify new information types that could assist them. A Mobile Accessible Pedestrian Signals (MAPS) prototype was developed to support decision making at signalized intersections. The MAPS integrates sensors on a Smartphone, Wi-Fi, and Bluetooth technologies, and traffic signal controllers were developed to provide intersection geometry information and Signal Phasing and Timing (SPaT) to pedestrians who are blind at signalized intersections. (Univesity of Minnesota. Center for Transportation Studies report CTS 11-11, June 2011, 135p.)

Dynamic Traffic Assignment - A Primer
This circular is designed to help explain the basic concepts and definitions of dynamic traffic assignment (DTA) models and addresses the application, selection, planning, and execution of a DTA model. The report also describes the general DTA modeling procedure and modeling issues that may concern a model user. (US Transportation Research Board Research Circular E-C153, June 2011, 62p.)

Safety (voir aussi Sécurité)

Safety Evaluation of Curve Warning Speed Signs
This report presents a review of a research effort to evaluate the safety implications of advisory speeds at horizontal curve locations on Oregon rural two-lane highways. The primary goals of this research effort were to characterize driving operations at rural two-lane highway curve locations where advisory speed signs were present, and to determine to what extent these signs play a role in enhancing safety. Placement of advisory speed signs at horizontal curve locations in the State of Oregon is a practice aided by unique and specific state-level policies and, as such, may vary from nationally accepted procedures. (Oregon Department of Transportation report FHWA-OR-RD 11-14, June 2011, 151p.)

The effect of better road delineation: a new method of assessment
In this research project, the innovative ‘hands-on’ method, first developed by Walton and Thomas in 2005, was tested in its ability to evaluate the effects of improved road delineation on driver behaviour. The method uses hand positions on the steering wheel as an indicator of drivers’ perceived risk, with drivers being more likely to place both their hands on the top half of the steering wheel when driving through a more difficult environment. The results showed that the ‘hands-on’ method was an effective and reliable tool to measure the impact of improved linemarkings on drivers, and to quantify the size of this effect compared with daylight driving. The method was sensitive to subtle changes in the road context, which makes it a useful instrument for road engineers to evaluate the relative improvement or change in drivers’ responses to changes in road contexts. (New Zealand Transport Agency research report 442, April 2011, 66p.)

Behavior Study of Merge Practices for Drivers at Work Zone Closures
The purpose of this project was to determine which driver behaviors result in the greatest reduction of capacity with work zone lane closures. Traffic and safety experts believe that driver behaviors, such as forcing late mergers, tailgating, queue jumping in the closed lane or on the shoulder, and other aggressive behaviors have the greatest impact on maximum flow rates. Other behaviors that create excessive headways or slow speeds can also reduce maximum flow in the taper. The objectives of this project were to identify and document driver behaviors that are the most detrimental to work zone traffic flow and safety. (Iowa State University Institute for Transportation report InTrans Project 09-359, June 2011, 64p.)

En route to safer roads; How road structure and road classification can affect road safety
The subject of this study is the influence of network structure and road classification on road safety. It is not evident how one can relate what happens at street level to the decisions regarding network design and the elaboration of this design. Traffic circulation can be regarded as the link between these two levels. Behind traffic circulation is the individual who decides to travel from a point of origin to a destination, using a particular route. The route is the starting point for this study. That is because network structure and road classification are important preconditions for traffic circulation and route choice, while the intersecting routes will determine the crash locations. This study will therefore focus on the effects of changing route choices on road safety. (SWOV Netherlands PhD Thesis, 2011, 247p.)

PRAISE: Preventing Road Accidents and Injuries for the Safety of Employees
The focus of this thematic report is improving safety for both employees and road users in relation to work zone areas on and adjacent to roads. The road work zone (RWZ) is defined as the part of a road facility influenced by works occurring on or near it. The report sets the context by outlining the nature and scope of the problem of road safety at road related work zones including identification of the most significant risk factors and causes of collisions and incidents. The Report then takes a specific look at the various stages involved in working on or near roads namely planning, operation, installation and removal of the works. At each stage key issues in terms of safety are identified and discussed. Subsequently good practice solutions or approaches in terms of RWZ safety have been identified and recommendations for the EU, National governments and Employers in terms of contributing to improved worker safety are suggested. (European Transport Safety Council (ETRC) report, May 2011, 42p.)

Structures (voir aussi Ouvrages d'art)

Cost-Effective Connection Details for Highway Sign, Luminaire, and Traffic Signal Structures
This report documents the results of a comprehensive experimental and analytical study that evaluated fatigue performance of several critical welded connections in the highway sign, signal and high-level luminaire support structures. In this study, infinite life fatigue resistance of connection details in the existing inventory was established and new cost-effective fatigue resistant connections were developed. About 80 full size galvanized specimens of sign, signal and high-level luminaire support structures containing different welded connections were fatigue tested. Using parametric Finite Element Analyses (FEA) of 3D models verified by test data, fatigue performance of the connections in both finite and infinite life regimes were defined in terms of fatigue stress concentration factors over the range of applicable geometric dimensions. The study demonstrated that tube-to-transverse plate connections are the most fatigue critical details in the subject structures. Increasing the stiffness of the transverse plate is the most costeffective means of improving fatigue resistance of this connection. Groove welded connections with smaller opening in the plate exhibits largest fatigue resistance. Sharper bend radius and less number of sides reduce fatigue threshold of connections in multi-sided sections. Based on these research findings, new specification recommendations were proposed for revision to the existing AASHTO specifications. (US Transportation Research Board National Cooperative Highway Research Program (NCHRP) Web-Only Document 176, March 2011, 236p.)

Performance Evaluation of One-Coat Systems for New Steel Bridges
In an effort to address cost issues associated with shop application of conventional three-coat systems, the Federal Highway Administration completed a study to investigate the performance of eight one-coat systems and two control coatings for corrosion protection of highway bridges. Based on prior performance, a three-coat system and a two-coat system were selected as the control coating systems. The performance of all coating systems was evaluated under accelerated laboratory and outdoor exposure conditions. A calcium sulfonate alkyd coating system was found to perform equally in comparison with the three-coat system; however, curing was a major concern. (US Federal Highway Administration report FHWA-HRT-11-046, June 2011, 104p.)

Effects of Fire Damage on the Structural Properties of Steel Bridge Elements
It is well known that fire can cause severe damage to steel bridges. However, when the damage is less severe, the effects of the fire, if any, are not so clear. Evaluation techniques that can be performed easily in the field, but still provide uniform and meaningful information for this situation are lacking. The objective of this research is to develop simple yet effective guidelines for assessing the potential level of damage sustained during a fire when there are no obvious signs of distress (i.e., sagging, collapse). The guidelines are intended to be used by inspectors and engineers in the field immediately following the fire event to provide general insight into the potential influence the fire may have had on the material properties of the bridge steel, based on the visual appearance of the steel. (Pennsylvania Department of Transportation report FHWA-PA-2011-009-PIT011, 30 April 2011, 62p.)

Evaluating the Time-Dependent and Bond Characteristics of Lightweight Concrete Mixes for Kansas Prestressed Concrete Bridges
This report details results from testing that was conducted to determine the bond and time-dependent characteristics of two lightweight concrete mixes. The lightweight mixes were evaluated to possibly provide a more cost-effective solution to replacing some of Kansas’ older bridges. Testing included use of a conventional lightweight mix and a self-consolidating lightweight mix. This study found the compressive strengths of the plant-cast lightweight concrete mixes varied greatly from similar mixes in laboratory testing. Low concrete strengths caused the prestress losses to be greater than the predicted code values. Flexural beam testing revealed that several of the pretensioned beams failed suddenly due to strand slip, even though this was not the predicted failure mode. (Kansas Department of Transportation report K-TRAN: KSU-08-2, July 2011, 130p.)

Administration (voir aussi Administration)

Benefits of new and improved pedestrian facilities - before and after studies
The NZ Transport Agency has recently updated the procedures for the evaluation of pedestrian improvement projects. The benefit factor applying to new pedestrian trips was increased from $0.50 to $2.70/km, making pedestrian facility improvement projects more economically viable. Thus, estimating the increase in pedestrian flows (as opposed to simply recording existing pedestrian flows) is now important in the economic evaluation of new or improved facilities. This research analysed case studies at eight New Zealand sites where the implementation of new pedestrian facilities (or the improvement of existing facilities) led to increased pedestrian usage and improved perception of the sites. The study recorded pedestrian rates both before and after facility implementation, and analysed accompanying factors such as safety, delay and directness. It also tried to develop an expected pedestrian-usage model, based on before and after data analysis, for planners and funding agents to use when planning new or improved facilities, and for use in project evaluation. (New Zealand Transport Agency research report 436, May 2011, 142p.)

Performance Measures for Complete, Green Streets
In California, a directive mandates that the California Department of Transportation (Caltrans) provide for bicycling and walking facilities along Caltrans’ roadways, thus creating Complete Streets, which are defined as “transportation facilit(ies) that (are) planned, designed, operated, and maintained to provide safe mobility for all users...” Performance measurement systems used by state DOTs to identify best practices were compiled and reviewed for roadside design elements. The performance measurement framework focused on arterial roadways where the greatest conflicts between motorized and nonmotorized traffic occur. The framework provides Caltrans with the supplementary measures needed monitor pedestrian and bicyclist safety and the environmental health of urban arterials. (University of California Transportation Center report UCTC-FR-2010-12, July 2010, 128p.)

Alternative Approaches to Funding Highways
About 25 percent of the nation's highways, which carry about 85 percent of all road traffic, are paid for in part by the federal government. Federal spending on highways comes primarily from taxes on gasoline and diesel fuel, but those and other taxes paid by highway users do not yield enough revenue to support current or proposed federal spending on highways. Although raising fuel taxes would increase revenue, those taxes alone cannot provide a strong incentive for highway users to consider all of the costs their road use imposes on others. This CBO study, prepared at the request of the Senate Budget Committee, examines broad alternatives for federal funding of highways, focusing on fuel taxes and on other taxes that could be assessed on the basis of the number of miles that vehicles travel. (US Congressional Budget Office report, March 2011, 38p.)

Financial Analysis of Transportation-Related Public Private Partnerships
On July 28, 2011 we issued a report on our financial analyses of transportation-related Public Private Partnerships (PPPs). Our objectives were to: (1) identify financial disadvantages to the public sector of PPP transactions compared to more traditional public financing methods; (2) identify factors that allow the public sector to derive financial value from PPP transactions; and (3) assess the extent to which PPPs can close the infrastructure funding gap. We found that PPPs have several financial disadvantages when compared to traditional public sector financing, however, certain private sector efficiencies can meaningfully offset PPPs' cost disadvantages. (US Department of Transportation. Office of the Inspector General report CR-2011-147, 28 July 2011, 28p.)

Requirements and Feasibility of a System for Archiving and Disseminating Data from SHRP 2 Reliability and Related Studies
This report provides an assessment of the feasibility of developing and populating an online archive for the great variety and volume of data being produced by the SHRP 2 Reliability focus area research program. The goal of the archive, if feasible, is to provide researchers and other interested parties with ready access to data needed to independently validate the results of SHRP 2 Reliability research and to conduct follow-on research. For this project, the term “data” was defined in the broadest way possible to include statistical data, analytical tools and models, written reports, pictorial data, and video data. (US Second Strategic Highway Research Progam (SHRP) 2 report S2-L13-RW-1, 2011, 79p.)

Bicycle Infrastructure that Extends Beyond the Door: examining investments in bicycle-oriented design through a qualitative survey of commercial building owners and tenants
This paper presents the results of a qualitative survey of commercial owners, managers, and occupants in the City of Berkeley who have invested in on-site bicycle facilities such as secure parking, showers, changing rooms, and clothing lockers, what we are calling “bicycle-oriented design” (BOD). The sites represent a selection of building types common in the commercial building stock in U.S. cities. The research is designed to answer three questions about the use of BOD: (1) what were motivations behind the decision to invest in BOD (2) what are the challenges and rewards for investing in BOD? and (3) what types of BOD were chosen? The survey was carried out through structured interviews and by site visits. (University of California Transportation Center report UCTC-FR-2011-03, February 2011, 12p.)

Cost of a Ride: The Effects of Densities on Fixed-Guideway Transit Ridership and Capital Costs
Through the investigation of more than 50 transit investment projects built in the U.S. since 1970, we find a strong correspondence between costs and ridership. Capital costs and ridership are positively correlated. Moreover, both ridership and capital costs typically rise with job and population densities. By clustering trip ends near stops, concentrated development tends to average far more transit trips per square mile than less concentrated development. But density often increases construction costs as well – via increased costs for right-of-way acquisitions and building demolitions, more complicated route alignments, utility relocation expenses, and higher labor costs. Are there densities that offer the most “bang for the buck” in terms of the number of riders for the investment costs? If so, what minimum densities should municipalities zone for around existing or planned stations in different settings or for different types of investments? (University of California Transportation Center report UCTC-FR-2010-32, August 2010, 29p.)

Transportation Intelligence

Volume 9 Number 5

Français

October 2011

Planning

Pavements

Traffic Control

Safety

Structures

Administration

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