bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Pedestrians on Capacity of Signalized Intersections
Authors: Milazzo Joseph S. , Rouphail Nagui M. , Hummer Joseph E. , Allen D. Patrick
Published: April 2007

In Chapter 9 of the 1994 update to the 1985 Highway Capacity Manual, the operational and planning analysis of signalized intersections is discussed. The methodology for saturation flow rate estimation does not consider all elements of the interaction between pedestrians and turning vehicles. This study describes this interaction for left and right turns using a conflict-zone-occupancy approach. A conflict zone is a portion of an intersection, typically in the crosswalk, in which pedestrians and vehicles compete for space. Conflict-zone occupancy, defined as the fraction of the effective green period during which pedestrians occupy a conflict zone, provides the basis for a rational adjustment to saturation flow. This study details the results of a multiregional data collection effort that confirms the validity of the conflict-zone-occupancy approach. In addition, this study describes the effect of geometric constraints, as reflected in the number of receiving lanes versus the number of turning lanes, on turning-vehicle saturation flow. After consideration of signalized intersection phasing and turn protection, one can calculate saturation flow adjustment factors reflecting the effect of pedestrians on lane groups containing vehicles turning left ( fLpb) or right ( fRpb).
Gap Acceptance Capacity for Right Turns at Signalized Intersections
Authors: Virkler Mark R. , Krishna Murli Adury
Published: April 2007

The capacity for right turns into gaps at signalized intersections, through right turn on red (RTOR) and free rights (with yield control), is examined. Current treatments provided by the Highway Capacity Manual (HCM), SIDRA, and a stop sign analogy (SSA) are examined. An adjustment to the SSA to eliminate capacity from gaps greater than the unsaturated flow period of the conflicting traffic is then described. The capacity for right turns into gaps is measured through a field study of seven right-turn-only lanes. The measured capacities are then compared with predicted capacities from the SSA and the adjusted stop sign analogy (ASSA). The data indicate that the HCM procedure to estimate RTOR volumes may not properly estimate those volumes. The SSA procedure tends to overestimate right-turn capacity by ignoring the effect of short phase lengths. The ASSA procedure provides lower estimates of capacity than the SSA, but may underestimate capacity. The results of the study can significantly increase the accuracy and usefulness of signalized intersection analysis by helping to answer questions about right-turn capacity, which now cannot be adequately addressed.
Analysis of Two Left-Turn Equations from the Highway Capacity Manual
Authors: Hurdle V. F. , Lord Dominique
Published: April 2007

The left-turn procedures in the Highway Capacity Manual are complex, and some of the equations are presented with little explanation of how they were obtained and the assumptions they embody. This paper is an analytic exploration of two of the four equations used to estimate gq, the amount of green time needed to discharge the opposing queue, and gf, the amount of green time available for through vehicles before the first left-turning vehicle enters the intersection. The investigation reveals surprising hidden assumptions underlying Equation 9-17 for gq, which lead to errors when the opposing flow includes left turns. In the case of Equation 9-20 for gf, the theoretical results are consistently about 5 s larger but otherwise in reasonable agreement with the empirical equation and provide insight into how it could be improved. An analytic approximation is offered either as a replacement or as a framework for an improved empirical model.
Effect of Bicycles on Capacity of Signalized Intersections
Authors: Allen D. Patrick , Hummer Joseph E. , Rouphail Nagui M. , Milazzo Joseph S.
Published: April 2007

Although much is known about the operation of signalized intersections, little or no empirical research has been conducted regarding the effect of bicycles on signalized intersection capacity. The purpose of this study was to accurately quantify the effects of bicycles on signalized intersection capacity through the videotaping of several intersections that had significant bicycle traffic. Through the videotaping of intersections in Davis, California, and Gainesville, Florida, a relationship was determined between bicycle volumes and the percent of the green phase during which bicycle traffic occupies a conflict zone between bicycles and right-turning motor vehicles. It was also determined that one can ascertain the total net occupancy due to pedestrians and bicycles by taking the overlapping effects between bicycles and pedestrians into account. Using this total occupancy due to bicycles and pedestrians, one can calculate a saturation flow adjustment factor ( fRph) that reflects the reduction in saturation flow, and ultimately lane group capacity, for lane groups containing vehicles making permissive right turns in the presence of bicycles and pedestrians. The proposed procedure yields lower saturation flows and capacities than the current Highway Capacity Manual (HCM) procedure. In other words, on the basis of empirical data, when combined with pedestrian effects, the impact of bicycles on the saturation flow of lane groups containing right-turning vehicles is probably more detrimental than previously believed, and the capacities of intersections with significant bicycle and pedestrian traffic may be overestimated by using the current HCM procedures.
Simulation Studies of Traffic Operations at Oversaturated, Closely Spaced Signalized Intersections
Authors: Messer Carroll J.
Published: April 2007

Traffic congestion continues to have a serious impact on the productivity of the nation’s transportation system. Signalized service interchanges in urban areas serve as a critical connection between freeway and arterial surface street systems. These facilities often experience serious congestion problems because of high traffic demands exceeding capacity and because of their common, closely spaced ramp terminals. Moreover, service interchanges are usually a part of a signalized cross arterial and may also have short spacings to adjacent signalized intersections. Major deficiencies exist in the analysis technology and software tools available for analyzing traffic congestion problems at oversaturated signalized interchanges and closely spaced arterial systems. Results are provided of an investigation into the nature of oversaturated systems and also undersaturated systems that may become congested (oversaturated) because of poor signal timing and deficient spacing between the signalized intersections. Although the initial research focus was on signalized service interchanges based on calibrated NETSIM simulations, the research results are also applicable to closely spaced signalized urban arterials. The research shows that traffic congestion is complex, but it can be characterized and modeled. An upper bound on signal control delay is provided for oversaturated arterial operations.
Fixed Instrumentation for Monitoring Scour at Bridges
Authors: Lagasse P. F. , Richardson E. V. , Schall J. D.
Published: April 2007

Research was conducted to develop, test, and evaluate fixed instrumentation that would be both technically and economically feasible for use in measuring maximum scour depth at bridge piers and abutments. A variety of scour-measuring and scour-monitoring methods were tested in the laboratory and in the field, including sounding rods, driven-rod devices, sonic depth finders (fathometers), and buried devices. Two fixed-instrument systems, a low-cost fathometer, and a magnetic slidingcollar device using a driven-rod approach, showed significant promise during initial testing. The project concentrated on installing and testing these two instrument systems under a wide range of bridge substructure geometry, flow, and geomorphic conditions. Both instrument systems met all of the mandatory and many of the desirable criteria established for this research. Cooperative efforts with state highway agencies proved that both systems can be installed with equipment and technical skills normally available to district-level department of transportation maintenance and inspection personnel. The project also provided installation, operation, and fabrication manuals for the low-cost sonic instrument system and magnetic sliding-collar devices.
Riprap Performance at Bridge Piers Under Mobile-Bed Conditions
Authors: Toro-Escobar Carlos , Voigt Richard , Melville Bruce , Chiew Meng , Parker Gary
Published: April 2007

Design criteria for riprap at bridge piers in rivers is based on the specification of a size, gradation, and cover that does not fail under an appropriately chosen flood flow. Experimental tests of riprap performance at bridge piers to date have relied on a configuration for which the ambient bed is not mobilized, that is, clear-water conditions. In the field, however, riprap is, as a rule, subjected to mobile-bed conditions during floods. Recent experiments by three cooperating research groups (University of Auckland, Nanyang University, and St. Anthony Falls Laboratory) indicate a heretofore unrecognized mechanism for riprap failure under mobile-bed conditions. When the flow is in the dune regime, the passage of successive dunes causes riprap that is never directly entrained by the flow to sink and disperse. Pier scour is realized as a consequence of these processes. In some cases, the depth of scour realized is not significantly less than that which would occur without riprap. When the riprap is fully underlain by a geotextile, edge effects can cause local removal of riprap, upturning of the geotextile, and general failure. When the riprap is underlain by a partial geotextile (i.e., one that covers an area less than the riprap), edge scour causes local sinking that anchors the geotextile. The sinking and dispersion of the rest of the riprap are greatly limited, and the riprap fails only when flow velocities are sufficient for direct entrainment. The experiments suggest improved design criteria for the installation of riprap in the field.
Regionalization of Precipitation Characteristics in Montana Using L-Moments
Authors: Parrett Charles
Published: April 2007

Dimensionless precipitation-frequency curves for estimating precipitation depths having small exceedance probabilities were developed for 2-, 6-, and 24-hour storm durations for three homogeneous regions in Montana. L-moment statistics were used to help define the homogeneous regions. The generalized extreme value distribution was used to construct the frequency curves for each duration within each region. The effective record length for each duration in each region was estimated using a graphical method and was found to range from 500 years for 6-hour duration data in Region 2 to 5,100 years for 24-hour duration data in Region 3. The temporal characteristics of storms were analyzed, and methods for estimating synthetic storm hyetographs were developed. Dimensionless depth-duration data were grouped by independent duration (2, 6, and 24 hours) and by region, and the beta distribution was fit to dimensionless depth data for various incremental time intervals. Ordinary least-squares regression was used to develop relations between dimensionless depths for a key, short duration—termed the kernel duration—and dimensionless depths for other durations. The regression relations were used, together with the probabilistic dimensionless depth data for the kernel duration, to calculate dimensionless depth-duration curves for exceedance probabilities from .1 to .9. Dimensionless storm hyetographs for each independent duration in each region were constructed for median value conditions based on an exceedance probability of .5.
Use of Weather Surveillance Radars—88 Doppler Data in Hydrologic Modeling
Authors: Curtis David C.
Published: April 2007

Successful hydrologic modeling depends heavily on high-quality rainfall data sets. If hydrologists cannot determine what is coming into a watershed, there is little chance that any hydrologic model will accurately estimate what is coming out on a consistent basis. Hydrologists are frequently forced to use rainfall data sets derived from sparse rain gauge networks that poorly resolve critical rainfall features, leading to inadequate model results. Over the past several years, the modernizing National Weather Service, the Federal Aviation Administration, and the Department of Defense have installed a new nationwide network of weather radars, providing a rich suite of real-time meteorological observations. Radar rainfall estimates from the new radars cover vast areas at a spatial and temporal resolution that would be impossibly expensive to match with a conventional rain gauge network. Hydrologists can now literally see between the gauges and view truer representations of the spatial distribution of rainfall than ever before. Results from the analysis of the January 9-10, 1995, storms in Sacramento, California, show that gauge-adjusted radar rainfall estimates help resolve rainfall features that could not have been inferred from rain gauge analysis alone. Accurate estimates of the volume, timing, and distribution of rainfall helped create excellent modeling results. In Waco, Texas, radar rainfall estimates were used to improve the analysis of excess inflow and infiltration into city storm sewers. The radar rainfall analyses enabled modelers to account for inflow/infiltration variations down to the neighborhood level.
Roadside Safety Analysis Program: A Cost-Effectiveness Analysis Procedure
Authors: Mak King K. , Sicking Dean L. , Zimmerman Karl
Published: April 2007

Brief descriptions are provided of a new cost-effectiveness analysis program, known as the Roadside Safety Analysis Program (RSAP), which was developed under NCHRP Project 22-9. RSAP is an improvement over existing cost-effectiveness analysis procedures for evaluation of roadside safety improvements, such as the procedures in the 1977 AASHTO barrier guide and the ROADSIDE program. RSAP improves on many of the algorithms in the procedures and provides a user-friendly interface to facilitate use. The program has undergone extensive testing and validation, including evaluation by an independent reviewer. It is anticipated that RSAP will be available to the public through the McTrans Center at the University of Florida.
Development of a Sequential Kinking Terminal for W-Beam Guardrails
Authors: Sicking Dean L. , Reid John D. , Rohde John R.
Published: April 2007

A new tangent energy-absorbing W-beam guardrail terminal that meets NCHRP Report 350 criteria has been developed. The terminal, designated the SKT-350, dissipates the energy of an encroaching vehicle by producing a series of plastic hinges in the W-beam as the terminal head is pushed down the guardrail. This energy-absorption concept allows for significantly lower dynamic forces on the encroaching vehicle, reducing the vehicle damage, the weight of the terminal head, the propensity for vehicle yaw and roll after impact, and the chances of buckling in the W-beam section. The energy required to move the head down the rail in this design is optimized for current criteria, but by modifying the bending geometry in the head, the average force to displace the head down the rail can be adjusted from values ranging from 11 to 60 kN (2,500 to 13,500 lb), meaning that the system can be easily modified to meet any future changes in safety performance standards. In addition to these important safety advantages, the terminal incorporates a unique cable anchor bracket that closely resembles a breakaway cable terminal anchor and a novel foundation tube design that facilitates the removal of broken posts during repair. Combining the features of reduced forces and head weight, a simple cable box, and more economical soil tubes allows the system to offer the advantages of both reduced cost and improved performance.
Development of a Three-Dimensional Simulation Model of Vehicle-Bridge Railing Crash: A Computer-Aided Approach to Bridge Railing Stiffness Design
Authors: Wang Yuqing , Tamura Yosuke , Ishikawa Hirotoshi , Ando Kazuhiko
Published: April 2007

To improve the conventional lengthy and inefficient design process for bridge railings, which features repetitions of costly full-scale experiments, and to support the bridge railing design with analytical data, this research developed a three-dimensional (3-D) simulation model that can reconstruct a vehicle-bridge railing impact analytically and visually using MADYMO (MAthematical DYnamic MOdel), developed by TNO. Both the vehicle and the bridge railing are modeled as rigid multi-body systems. A nonlinear tire model and a 3-D suspension are introduced to increase the reality of the vehicle motion during impact. The bridge railing is divided into poles and longitudinal railings. The bending characteristics of the poles and the longitudinal railings are described by the properties of corresponding universal joints attached to them. The simulation model is verified by experimental data of three different conditions using heavy trucks (8 tons and 20 tons). The validation reveals that the 3-D model can reconstruct vehicle-bridge railing crashes with a high degree of accuracy with respect to the vehicle performance and the deformation of the bridge railing, which are the most important concerns in the designs of bridge railings. The validated crash model is then employed to determine the necessary stiffness of the bridge railing under different conditions. Curves describing the relationship between the stiffness of the poles and the longitudinal railings are calculated for various impact severity values. These curves provide analytical grounds for the stiffness designs of the bridge railings.
Approach Guardrail Transition for Concrete Safety Shape Barriers
Authors: Faller Ronald K. , Reid John D. , Rohde John R.
Published: April 2007

An approach guardrail transition for use with concrete safety shape barriers was developed and crash-tested. The transition was constructed with two nested thrie-beam rails, measuring 2.66 mm thick, and supported by nine W150 x 13.5 steel posts. Post spacings consisted of one at 292 mm, five at 476 mm, and three at 952 mm. Structural tube spacer blockouts were used in the transition system. The system successfully met the Test Level 3 requirements specified in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features.
Model of the Performance of a Roadway Safety Fence and Its Use for Design
Authors: Bateman Mark B. , Howard Ian C. , Johnson Andrew R. , Walton John M.
Published: April 2007

The optimization of roadway safety design by experimental means is expensive and time consuming. Computer simulation of such complex engineering systems improves understanding of how and why the system behaves as it does, aids in decision making, and reduces development costs and time involved. The simulation presented is based on a computer model developed from a study of the results of full-scale experiments of impact on the Brifen wire-rope safety fence (WRSF). The code comprises a dynamic vehicle model and a quasi-static fence model interacting in time through the important collapse mechanisms of the system. The principles governing them are described and their inclusion is validated by demonstrating good correlation between the predictions of the simulation and the experimental test data. Sensitivity studies show that the performance of a WRSF is particularly sensitive to the impact conditions of vehicle speed and angle and the design parameters offence height, post spacing, post strength, and rope pre-tension. The sensitivity work is extended to show that for fences installed with a low rope pre-tension, performance may not be significantly impaired if rope pre-tension is not maintained. However, significant gains in fence performance may be made should a fence be installed and maintained with a high rope pre-tension. The use of the simulation in assessing cost-effectiveness of alternative designs in achieving a target performance is also demonstrated.
Finite-Element Modeling and Model Verification of Steel W-Beam Guardrails Subject to Pendulum Impact Loading
Authors: Gentry T. Russell , Bank Lawrence C.
Published: April 2007

The experimental and simulated response of steel W-beam guards to pendulum impact loading for impact velocities of 20 km/h, 30 km/h, and 35 km/h are presented. The guardrails were supported by four posts and cable-anchored at each end to ensure that the full tension capacity of the rail could be developed. Experiments carried out with a 912-kg impact pendulum are compared with LS-DYNA finite-element simulations of the impact events. Pendulum tests were completed at the Turner Fairbank Highway Research Center of the Federal Highway Administration. Acceleration, velocity, and displacement time histories are compared for the pendulum impact test and the LS-DYNA simulations. Comparison of the experimental and simulation acceleration records is made using the Numerical Analysis of Roadside Design time-domain statistics. The comparative statistics show that the simulations are in good agreement with the experiments. Guardrail tension data and cable tension data are presented from the LS-DYNA simulations. Results show that the guardrail was close to its tension yield point when impacted an initial velocity of 35 km/h.
Plan of Action To Reduce Vehicle-Train Crashes in Alabama
Authors: Bowman Brian L. , Stinson Kristen , Colson Cecil
Published: April 2007

In April 1996, the state of Alabama Legislature, through the passage of Act 503, directed the Alabama Department of Transportation (ALDOT) to conduct a comprehensive study of rail-highway grade crossings in the state and recommend methods to drastically reduce the number of vehicle-train crashes. Senate Act 503 states: “… That the Alabama Department of Transportation is directed to conduct a comprehensive study of the rail/highway grade crossings in the state and present a plan to this body recommending methods to dramatically reduce vehicle/train accidents by the first day of the 1997 Regular Session.” In response to Act 503, the Multimodal Bureau of ALDOT developed an Action Plan that compared Alabama’s grade crossing crash experience with the experience of the national and southeastern states to identify the prevalent characteristics, identified the perceived needs of safety and railroad professionals required to decrease vehicle-train crashes and crash severity, and compiled a list of recommendations and activities required for implementation. The activities and results of the Act 503 study documented in the final report are summarized (1). It discusses the engineering, economic, educational, enforcement, and emotional impediments to increasing rail-highway intersection safety and presents a broad range of realistic countermeasures. These countermeasures include legislative action; judicial reform; and enforcement, economic, and education initiatives.
Enhanced Traffic Control Devices at Passive Highway-Railroad Grade Crossings
Authors: Noyce David A. , Fambro Daniel B.
Published: April 2007

More than 2,000 crashes and 239 fatalities were reported at public passive highway-railroad grade crossings in 1994. Driver error, often due to a breakdown in communication between traffic control devices and the driver, is commonly cited as a factor in passive grade crossing crashes. The objective of this study was to evaluate an improved method for communicating with drivers in an effort to improve safety at passive grade crossings. Specifically, this study evaluated the effectiveness of a vehicle-activated strobe light and supplemental sign as enhancements to the railroad advance (W10-1) warning sign at a passive highway-railroad grade crossing near Temple, Texas. Three study methods were used to evaluate this enhanced sign system including a before and after speed study, a driver survey, and a driver observation study. The results indicated that average speeds on the approaches to the grade crossing were lower after the installation of the enhanced sign system. Drivers responded favorably to the enhanced sign system, and no adverse driver reactions were observed at the onset of the flashing strobe light. The strobe light was effective in directing drivers’ attention to the railroad advance warning and supplemental signs. The enhanced sign system appears to increase driver awareness of the passive grade crossing, cause some drivers to approach the grade crossing with additional caution, and reduce the average speed near the nonrecovery zone on both approaches.
Risk Assessment of Competitive Procurement on Alabama Highway Projects with Texas Comparisions
Authors: Crowley Larry G. , Madewell Jared L.
Published: April 2007

Public agencies generally let construction contracts to the lowest responsible, responsive bidder. In following this practice, agencies recognize there are higher risks of cost growth in awarding to either unusually low bids or to certain “claim-conscious” bidders. Despite this awareness, there are few documented studies supporting or quantifying the presence of these perceived competitive procurement risks. This research undertakes that specific task. First, bids and bidders on a sample of Alabama highway projects are grouped into risk categories by information available at the project bid opening—well in advance of any potential contract award— and without considering actual project performance data. Second, the cost growth experiences of these projects are statistically analyzed based upon these risk groupings. The results indicate that cost growth on Alabama highway projects is significantly more likely when projects are awarded to unusually low bids or to certain bidder types. A similar study performed earlier on Texas highway projects provides nearly identical results. This type of analysis and the derived information can be used by public agencies to amend the procurement process and objectively disqualify unusually low bids or questionable bidders without abandoning competitive procurement principles.
Pragmatic Approach to Finance Infrastructure: Analysis of French Experience with Highway Concessions
Authors: Fayard Alain , Bousquet Franck
Published: April 2007

Governments around the world are showing increasing interest in concessions or build-operate-transfer mechanisms in the highway sector. One or two decades ago, economic theory held that private funding was the most promising method for financing infrastructure development. Unfortunately, a significant number of privately financed projects are showing signs of difficulties (e.g., the Franco-British Channel Tunnel, the Dulles Greenway in Virginia, the second stage Bangkok Expressway in Thailand, the Guanzhour-Shenzen Highway in China, the delayed Birmingham Northern Relief Road in the United Kingdom, and the M1 and M3 Highways in Hungary). Emphasis has always been put on the financial aspect, leaving out the organizational one. A new basis for infrastructure finance is presented, analyzing the mistakes and successes of French experience in highway concession for more than 40 years. This experience is of interest since France has experimented with both toll and nontoll financing as well as with publicly and privately owned toll roads in building its system of highways. The main steps of the construction of the French highway network through concessions are traced and the lessons learned from this experience indicated, focusing on key elements, the advantages and drawbacks of a concession system, and the exact nature of the state’s role in concessioning. This information can serve as potential recommendations for other countries opting for concession systems.
Evaluation of Two Tolling Strategies for Highway 407 in Toronto
Authors: Mekky Ali
Published: April 2007

Two tolling strategies were recently suggested for Highway 407 in the Greater Toronto Area (GTA). The GTA is one of the fastest growing urban areas in North America with a population of about 5 million. Highway 407, a six-/four-lane freeway, has been considered for many years as a relief for Highway 401—the busiest highway in North America, used by more than a million vehicles per day. Highway 407 is being planned and constructed as a toll highway. The first strategy investigated is to encourage long distance travelers to use Highway 407 by reducing the toll rate from CD$0.075/km to $0.06/km after the first 10 km. This is modeled by using multiclass trip assignment with generalized cost. Aside from the class of drivers who are not going to use the highway for various personal reasons, there are two main classes of drivers—namely, drivers who travel 10 km or more, and those who travel less than 10 km. The second strategy investigated is to put extra tolls on Highway 407 ramps connecting the highway with widened Highways 427, 400, and 404. The purpose of the second strategy is to recover the cost of widening these highways near Highway 407 through ramp toll revenues. The GTA mathematical model, within the EMME/2 environment, and the evaluation process used are described. Evaluation results are discussed.
Devolution of Surface Transportation: Preliminary Assessment of Revenue and Financial Aspects
Authors: Beshers Eric , Hayduk Brian , Noland Robert B.
Published: April 2007

Recently, the topic of devolution of the federal role in surface transportation has been actively discussed. The impact on state finances, however, has not yet been analyzed. The way in which a reduction in federal transportation funding (as envisioned by legislation recently proposed by Rep. John Kasich and Sen. Connie Mack) would affect state financing is examined in this paper. This is combined with an assessment of states’ need for financing and their ability to make up any funding shortfalls. The results of this analysis indicate that, although most states would require smaller increases in their fuel taxes than the drop in federal taxes, many would have difficulty making up this shortfall. Many of these same states also have a great need to maintain their transportation infrastructure. Even if the specific issues were to change were devolution imminent, this research provides a useful analysis of the financial issues. A brief discussion of the possible environmental effects of devolution and reduced highway spending is included.
Stated Response Analysis of the Effectiveness of Parking Pricing Strategies for Transportation Control
Authors: Kuppam Arun R. , Pendyala Ram M. , Gollakoti Mohan A. V.
Published: April 2007

Transportation control measures based on parking pricing strategies have been receiving considerable attention in many urban areas. Parking pricing entails the levying of a surcharge or tax for parking a personal vehicle that may vary by location and time of day. Stated responses to parking pricing scenarios were obtained from a survey sample of 656 commuters in the Washington, D.C., metropolitan area. Two parking pricing strategies are analyzed. The first strategy involves the imposition of a parking surcharge alone; the second involves the imposition of a parking surcharge together with the provision of an employer-paid transportation voucher. A detailed descriptive analysis of commuter response to parking pricing strategies is presented, and the response distributions in relation to various socioeconomic, demographic, and travel characteristics are analyzed. In general, parking pricing–based strategies are found to exhibit the potential to serve as effective transportation control measures. The employer-paid transportation voucher, although resulting in switches in behavioral responses for a substantial number of commuters, had little impact on the marginal response distributions.
California Route 91 Toll Lanes Impacts and Other Observations
Authors: Sullivan Edward C. , Harake Joe el
Published: April 2007

The 16-km (10-mi) long California State Route 91 (SR-91) variable-toll lanes entered service December 27, 1995. This facility is the first practical application of congestion-based road pricing attempted in the United States. The California and U.S. Departments of Transportation sponsored a study to observe how travelers respond over time to variable-toll pricing and the other innovative features of this unique facility. Data covering a wide range of travel and transportation issues were obtained from mid-1994 through June 1997 and analyzed for lessons to inform public policies about future applications of congestion-based pricing. The principal findings are summarized. The SR-91 toll lanes are regarded as a success in terms of both commuter acceptance and favorable opinions. Although, as expected, first-year toll revenues did not cover total annualized costs, the facility operator anticipates profitability in the near future. Impacts on corridor traffic have been positive, and, despite changes in traffic composition, the overall level of ridesharing has not been adversely affected. Fears that peak congestion-based tolls might preclude benefits to low-income commuters have not materialized, although a relationship was found between frequency of toll lane use and income level. No adverse traffic operational impacts were observed. From experience with the SR-91 variable-toll lanes, further careful experimentation with congestion-based pricing in other settings appears warranted.
The Planning of Toll Roads—Do Public Attitudes Matter?; Case of the Oslo Toll Ring
Authors: Odeck James , Bråthen Svein
Published: April 2007

In most countries, decisions on major infrastructure projects are most often carried out after a comprehensive public debate, especially when involving user payments. A time-series interview survey for the period 1989 to 1995 is used to review the Oslo toll ring scheme and determine and explain the public’s attitudes toward the scheme. A multivariate model is developed to isolate factors that affect users’ attitudes toward tolls. The results reveal that, although a majority of commuters oppose the toll system, the gap between those who are against and those who are in favor of the toll ring system is narrowing as the years go by. This narrowing process is analyzed. It is concluded that to achieve greater acceptability for tolling in road infrastructure funding, a more comprehensive range of targeted marketing efforts is required. Finally, a set of points of direct relevance for planning and marketing of future toll projects is proposed.
Comparing Approaches for Valuing Economic Development Benefits of Transportation Projects
Authors: Weisbrod Glen , Grovak Michael
Published: April 2007

Transportation agencies often face uncertainty regarding how to define and assess the economic magnitude of benefits associated with alternative projects and programs. Alternative types of economic impact analysis are examined, using data from a highway study in Kentucky to explore (1) differences in the definitions of economic benefits inherent in the various types of analysis, (2) reasons for their differing findings on the value of benefits, and (3) issues affecting their interpretation and use in decision making.
Travel Costs and Intermodal Distribution in Urban Transportation
Authors: Vuchic Vukan R. , Lee Young-Jae , Eun Shin Yong
Published: April 2007

The free selection of travel between automobile and transit modes results in the individual equilibrium condition, which is not socially optimal. It is shown that shifting travel from cars to transit under most conditions results in travel improvements for both modes. To implement this winwin change, however, it is necessary to decrease the disutility (cost) of travel by transit and increase the disutility of automobile travel. A comparative analysis of travel costs by different modes shows that automobile users pay extremely low out-of-pocket costs, particularly when parking is subsidized (free). Indirect costs and impacts of automobile travel in urban areas are very high, but users do not pay them. This condition of underpriced automobile use results in excessive driving, which causes traffic congestion and has many negative impacts on cities. In many cities, transit improvements or incentives are paralleled by automobile incentives; this represents subsidization of competing services and thus fails to induce modal shift. A shift of travel from cars to transit (and other modes) can best be achieved by car disincentives complemented by transit improvements, so that travelers can change modes rather than reduce essential trips. The mobility of the low-income population can be enhanced when revenue from automobile disincentives is applied to improvements of alternative modes. Measures that reduce subsidies to automobile use and convert them into direct user costs, such as a significant increase in gasoline taxes and a reduction of tax exemptions for many car trips, are both effective and equitable.
VDOT Is Moving in a New Direction: How Virginia’s Department of Transportation Is Using Strategic Management To Revamp Its Entire Operation
Authors: Sorrell Constance S. , Lewis Joseph F.
Published: April 2007

Leaders within Virginia’s Department of Transportation (VDOT) realized that the department would not be able to meet future challenges if it relied only on tactical responsiveness. VDOT embarked on a strategic management effort focused on shifting the organization’s culture to strategic thinking and customer responsiveness. The change effort began by drafting a new organizational vision, using purpose, mission, and values statements as guidelines for thinking strategically and meeting organizational goals. VDOT determined critical success factors and established performance measures to monitor these factors. Through a rigorous strategic planning process, leadership established overall departmental goals. VDOT leadership created organizational alignment by implementing this process throughout its field locations. The result of this effort is a proactive, customer-focused organization with a culture for thinking strategically, acting locally, and performing at improved heights.
Performance Measure Initiative at the Texas Department of Transportation
Authors: Doyle Dawn
Published: April 2007

Since 1993 the Texas Department of Transportation (TxDOT) has initiated several activities to provide better government. One of the initiatives has been the use of measurement as a tool to guide behavior and evaluate performance. TxDOT implemented the performance measurement initiative at two levels. The first application was at the statewide level using TxDOT’s Strategic Plan; the second application was at the district and division levels through the creation of operational-level strategic plans. In the larger context of better government, measurement supports performance management by aligning strategic action, planning, and consequences with performance.
Service Life and Life of Service: The Maintenance Commitments
Authors: (Gray)Byrd L. G.
Published: April 2007

The magnitude of today’s highway maintenance challenge, the impact of research on maintenance, basic objectives that should drive a maintenance program, and the progress made in meeting them over the last 4 decades are discussed. Highway maintenance should include the objectives of providing a consistently safe, comfortable, and efficient travel way for highway users and a safe environment for maintenance crews; providing optimum service life; maintaining as-built capacity and reliability; inviting, supporting, and using research and innovation; and performing with professionalism, competence, and diligence. Some of the challenges in meeting these objectives today are accelerating rates of deterioration, limited time available to work, complex interchanges and crowded rights-of-way, environmental restrictions, a litigious society, and public skepticism about all government functions. Three categories of responses are technologies, policies, and professionalism. A significant array of new, innovative tools and other products of research are making maintenance technology more effective. Maintenance managers need to be activists in promoting progressive policies in providing as-built capacity while performing maintenance and repair work and in procuring products and services. Maintenance policies should include recognition of user costs, use of performance specifications, fabrication of off-site repair components, design of repairable highway systems, use of corrosion-resistant materials, privatization of segments of the maintenance program, and establishment of an international maintenance technology reference program. Individual professionals must embrace continuing education, environmental sensitivity, community service, research and development, innovative management, and societal and political responsibilities.
Impacts of Maintaining Traffic Signs Within Minimum Retroreflectivity Guidelines
Authors: Taori Sunil , Mcgee Hugh W.
Published: April 2007

The Federal Highway Administration has developed guidelines for minimum levels of retroreflectivity for four groups of signs: ( a) black-on-yellow/orange warning signs, ( b) black-on-white regulatory or guide signs, ( c) white-on-red regulatory signs, and ( d) white-on-green guide signs. The impact of implementing these guidelines was assessed by estimating the percentage of signs not meeting the proposed minimum levels and the cost of replacing such signs. Various state and local highway agencies assisted in the study by measuring the retroreflectivity of a sample of in-use signs, providing data on sign replacement costs, and commenting on the practicality of maintaining signs at minimum retroreflectivity levels. In general, the local agencies will have a higher percentage of signs needing replacement due to noncompliance with the minimum retroreflectivity guidelines than the state agencies, primarily due to a higher percentage of older and engineering-grade sheeting signs in service under their jurisdiction than the states. Overall, about 5.5 percent of the nation’s signs will not meet the minimum guidelines. About 8 percent of the local signs and about 4.5 percent of those under state jurisdictions will need replacement. Although warning signs will be the most critical signs for local agencies, the guide signs will be most critical for the states, each group requiring over 9.5 percent of the signs replaced. If all the signs not meeting the minimum guidelines are replaced, it would cost about $32 million to all the state agencies combined and about $144 million to the local agencies.
Crash Testing and Evaluation of Work Zone Barricades
Authors: Bligh Roger P. , Mak King K. , Rhodes Lewis R.
Published: April 2007

Proper traffic control and delineation are critical to achieving safety in work zones. However, the work zone traffic control devices themselves may pose a safety hazard to vehicle occupants or work crews when impacted by errant vehicles. Thus, there was a need to research the safety performance of work zone traffic control devices to ensure that they perform satisfactorily and meet NCHRP Report 350 guidelines. Several research studies sponsored by the Texas Department of Transportation evaluated the impact performance of various work zone traffic control devices, such as temporary and portable sign supports, plastic drums, sign substrates for use with plastic drums, traffic cones, and vertical panels. Specifically addressed are the studies on barricades. Standard wooden barricade construction was found to be unacceptable due to a demonstrated potential for intrusion of fractured members into the occupant compartment. In response to deficiencies identified in the wooden barricade tests, several alternate barricade designs were developed and successfully tested.
New Vehicle Data Bus Architecture and In-Vehicle Information System Evaluation Platform for Intelligent Transportation Systems Modules
Authors: Spelt Philip F. , Kirson Allan M. , Scott Susan
Published: April 2007

An increasing number of intelligent transportation systems- (ITS-) after-market systems present a set of in-vehicle installation and use problems relatively unique in the history of automobile use. Many automobile manufacturers would like to offer these new state-of-the-art devices to customers, but are hampered by the current design cycle of new cars. While automobile manufacturers are indeed using multiplex buses [the automotive equivalent of a computer local area network (LAN)], problems remain because manufacturers are not converging on a single bus standard. A new dual-bus architecture to address these problems is presented with an in-vehicle information system (IVIS) research platform on which the principles embodied in the ITS data bus architecture can be evaluated. The dual-bus architecture has been embodied in a proposed Society of Automotive Engineers (SAE) standard, with support from both automobile and consumer electronics manufacturers. The architecture and a reference model for the interfaces and protocols of the new bus are presented and described. The goals of the ITS data bus are to be inexpensive and easy to install, and to provide for safe and secure functioning. These high-level goals are embodied in the proposed standard. The IVIS development platform comprises a number of personal computers (PCs) linked via ethernet LAN, with a high-end PC serving as the IVIS computer. In this LAN, actual devices can be inserted in place of the original PC that emulated them. This platform will serve as the development and test bed for an ITS data bus conformity test, the SAE standard for which is also being developed.
Application of Fuzzy Logic to the Control of a Pedestrian Crossing Signal
Authors: Niittymaki Jarkko , Kikuchi Shinya
Published: April 2007

Fuzzy logic is known to be suited for dealing with a complex optimization problem with many objectives, many constraints, unclear input information, and vague decision criteria. Controlling the timing of a traffic signal falls in this category of problem. Fuzzy logic is introduced for controlling the timing of a pedestrian crossing signal. The controller is designed to emulate the decision process of an experienced crossing guard. The performance of this control is tested against two types of conventional demand-actuated control: one that uses the traditional green extension and the other that uses modified extension rules. The criteria for evaluation are delays to the pedestrians and the vehicles, and the percentage of vehicles that are stopped. The fuzzy logic controller finds a compromise between two conflicting objectives: minimization of pedestrian delay and minimization of vehicular delay and stops. The evaluation was performed using a microscopic simulation called HUTSIM developed at the Helsinki University of Technology. The fuzzy logic controller performs equally well as or better than conventional demand-actuated control without requiring many parameter settings. Furthermore, the control rules are simple and a compilation of rational decision processes is expressed in natural language.
Short-Term Freeway Traffic Volume Forecasting Using Radial Basis Function Neural Network
Authors: Park Byungkyu , Messer Carroll J. , Urbanik Thomas
Published: April 2007

A radial basis function (RBF) neural network has recently been applied to time-series forecasting. The test results of an RBF neural network in forecasting short-term freeway traffic volumes are provided. Real observations of freeway traffic volumes from the San Antonio TransGuide System have been used in these experiments. For comparison of forecasting performances, Taylor series, exponential smoothing method (ESM), double exponential smoothing method, and backpropagation neural network were also designed and tested. The RBF neural network model provided the best performance and required less computational time than BPN. It seems that RBF and ESM can be a viable forecasting routine for advanced traffic management systems. There are some tradeoffs between RBF and ESM. Although the performance of ESM is inferior to RBF, the former does not need a complicated training process or historic database, and vice versa. However, even in the best performance case, 35 percent of the forecast traffic volumes showed 10 percent or more percentage errors. This means that we cannot heavily depend on the forecast traffic volumes as long as we are utilizing the models tested. Further work is needed to provide a more reliable traffic forecasting model.