Driving simulator use and calibration for work zone merge sign evaluation

The guidelines for minimum visibility distance in the 2003 Manual on Uniform Traffic Control Devices (MUTCD) are based on a research model developed in 1977, a portion of which was based on stopping sight distance concepts from 1965. Since then, roadway design criteria, vehicle performance characteristics, and driver characteristics have changed. These changes provide justification for reevaluating the guidelines for minimum signal sight distance. This paper identifies the basis for the current guidelines (which were not published) and develops updated guidelines for signal sight distance. As with the original guidelines, the updated guidelines are based on a theoretical model that addresses reaction time, braking distance, and queue length. The key changes incorporated into the updated model are calculating the stopping distance on the basis of deceleration rates, using a reaction time consistent with the AASHTO stopping sight distance, and eliminating the provision for a vehicle queue at the stop line, as the driver should be able to respond to the queue on the basis of the stopping sight distance provided by the road. The updated values for minimum signal sight distance are typically 20% to 25% less than those currently in the MUTCD. The lack of guidance in the MUTCD about placement of the “Signal Ahead” sign is also pointed out, and it is suggested that it be located on the basis of the signal sight distance and not according to warning sign placement guidelines.

Fluorescent strong yellow-green (SYG) is one of the most unassigned colors in the Manual on Uniform Traffic Control Devices (MUTCD). FHWA has recently been considering the SYG color for nonmotorized application in the W11-2 series of signs in MUTCD. A number of field evaluation studies on the impact of these warning signs on conflicts and user preferences have been undertaken. A controlled-environment evaluation of the SYG pedestrian-crossing sign prototypes under five different natural light conditions is presented. Factors that contribute to different driver performance in response to microprismatic fluorescent SYG signs relative to the commonly used enclosed-bead yellow signs are identified. Target value and legibility distance of the prototypes in a simulated driving environment on a pool of test subjects are assessed. A factorial analysis of variance design was used to obtain unbiased estimates of these parameters. The general linear model was used iteratively to eliminate factors that did not affect...

This project evaluated the effectiveness of symbol traffic signs for young, middle-aged and elderly drivers. Daytime legibility distance and comprehension of 85 symbols in the Manual on Uniform Traffic Control Devices (MUTCD) were measured. Legibility distance under night and night-with-glare conditions, glance legibility, reaction time and conspicuity were measured for 18 of these symbols. Selected symbols were modified or redesigned and five novel symbols were designed, using an image-processing iterative filter-design approach. These new signs were evaluated on measures of comprehension and legibility distance under day, night and night-with-glare conditions. Of the 85 symbols many were well understood, but 10 were understood by fewer than 40% of drivers. Increased driver age was associated with lower comprehension levels and legibility distances (under all test conditions), as well as higher glance legibility thresholds, reaction times and conspicuity search times. Modifications and redesigns to the symbols resulted in better understanding of three messages and improved daytime legibility distances of 11 of the new signs. Glare reduced legibility of the signs only for the elderly drivers. recommendations were made for changes to specific symbol signs. Guidelines were proposed for the design of symbol traffic signs, and a proposal was made for design optimization techniques to be employed in the future development and evaluation of such signs.

Guide sign is an important traffic management facility and informs the drivers of road network information. It also has great impact on the smooth flow and traffic safety. This article draws on the construction method of conventional roads guide signs system from Manual on Uniform Traffic Control Devices (MUTCD). Based on the recognizing characteristic and the information retrieval model of Chinese drivers, this research provides the construction method of Chinese conventional roads guide signs system combined with the feathers of the Chinese road network structure. Using this method to the typical road network, the comparison and analysis of vehicle road experiments before and after reconstruction shows this method can effectively direct the drivers to improve the efficiency of arriving at the destination and reduce the probability of taking the wrong path. Based on this effect, it can be considered the effectiveness of guide signs designing is improved. (Programme No: 2009BAG13A02)

The geometric design of highway elements is based on a set of standards that do not consider the risk levels associated with these designs. Safety elements including risk measures need to be identified and incorporated into the design process. The focus of this paper is a procedure that can be used by practitioners as a framework to conduct trade-off analyses between risk and service measures of specific design elements. The procedure builds on the randomness of parameters affecting the design attributes of any highway element. By accounting for the inherent variability of the determining parameters, random distributions of the design element can be derived. Then, using stochastic simulation, each of the design values can be tested to assess its risk measures. As a result, a risk index can then be attached to every design value in the random distribution. Finally, level of service (LOS) measures can be estimated and a trade-off analysis between LOS and safety could be conducted. The application focused on the design of the passing sight distance (PSD), which is an example of a highway element traditionally analyzed with no risk measures. Within the analysis, the risks and LOS measures associated with the use of the current PSD standards were assessed. The American Association of State Highways and Transportation Officials (AASHTO) Green Book values were shown to be conservative. The Manual on Uniform Traffic Control Devices (MUTCD) values fall within the acceptable risk and level of service (LOS) levels. Language: en

ABSTRACTWith the concerns over the greenhouse gas (GHG) emissions associated with the surface transportation, the environmentally sustainable traffic signal warrant is essential to provide guidelines for making environmentally conscious decisions about control types at intersections. This research conducted a pilot study on developing CO2 emissions-oriented traffic signal warrants. Intersection control types that were analyzed for this research include two-way stop, four-way stop, traffic signal, and roundabout. Two environmentally sustainable traffic signal warrants were proposed: Type I (without roundabout) and Type II (with roundabout). The proposed traffic signal warrants were compared with the existing mobility-oriented traffic signal warrant of the Manual on Uniform Traffic Control Devices (MUTCD) in terms of CO2 emissions and total delay. The measurements were collected and estimated using a microscopic traffic simulation tool, Verkehr In Stadten—SIMulationsmodell (VISSIM). The environmentally sustainable traffic signal warrants show that the annual CO2 emissions of the ground transportations in the USA were reduced by 7.2% with Type I warrant and 13.9% with Type II warrant.

Truck safety evaluation on Wyoming mountain passes

Freeway work zones with lane closures can cause traffic disruption and congestion with increased travel time, safety risks, and emissions.Variable speed limit (VSL) control has been widely studied to mitigate the negative impacts of work zone lane closures.To ensure effective VSL control, accurate detection of traffic conditions is important.However, stationary sensors from distant upstream or merging areas of a work zone can only provide location-based detections, which may not be sufficient for effective VSL control.Therefore, this study proposes a VSL control system for a smart work zone with a weighted traffic density estimation algorithm using data from stationary sensors and connected vehicles (CV).With location-based traffic detections from distant upstream and merging areas of a smart work zone, data from CVs in locations between the stationary sensors are used to obtain the weighted density.This weighted density is then fed to a feedback VSL controller, which can dynamically define the appropriate speed limits to reduce the negative impacts of the work zone closures.The proposed VSL controller was implemented and evaluated under a calibrated freeway work zone environment using the traffic simulator SUMO.The results show that the system can provide accurate traffic density estimation and effectively improve traffic mobility, safety, and environmental sustainability near the work zone area.

Law enforcement presence in work zones has long been recognized as one of the most effective speed-reduction methods available to transportation officials. Unfortunately, the design of many work zones makes effective enforcement difficult. Work zones that have no emergency shoulders on either side of the roadway are especially problematic. Incorporating enforcement pullout areas into construction phasing plans has been suggested as a way to improve enforcement activities. However, no guidance had been available on how frequently such enforcement areas should be incorporated. Research was conducted to determine law enforcement and contractor opinions on acceptable spacing criteria for pullout areas in a highway work zone. Two sets of surveys were made by using the Delphi method to solicit the opinions of law enforcement officers and roadway contractors regarding the relative difficulty or effectiveness of pullout areas located at various spacings through a long work zone. The Delphi method was used to quickly bring these groups to consensus. Construction contractors generally were against placing pullout areas closer than 2 mi apart. By contrast, law enforcement officers indicated that at spacing greater than 3 mi, the pullout area would not be useful for traffic enforcement. The results indicate that enforcement pullout areas in work zones should be spaced approximately every 2 to 3 mi or, as an alternative, work zones that eliminate emergency shoulders that are adequate for enforcement purposes should be no longer than 3 mi.

Central to the effective design of work zones is being able to understand how drivers behave as they approach and enter a work zone area. States use simulation tools in modeling freeway work zones to predict work zone impacts and to select optimal design and deployment strategies. While simple and complex microscopic models have been used over the years to analyze driver behavior, most models were not designed for application in work zones. Using data collected from an instrumented research vehicle and model components from two PhD dissertations, FHWA created the Work Zone Driver Model and programed the Work Zone Driver Model DLL v1.0, a software that could override car-following in commercial microsimulation software packages so that practitioners can better predict work zone impacts. This paper demonstrates the capabilities of the FHWA Work Zone Driver Model DLL v1.0, interfaced with VISSIM and tested on an Interstate work zone in Springfield, Massachusetts. The dynamic link library’s (DLL’s) performance is compared with field data collected using an instrumented research vehicle and to Weidemann 99 in VISSIM. Performance metrics were selected to align with state department of transportation work zone management efforts. Results showed acceptable performance from the DLL, as it predicted queue locations and travel speeds that were near field observations. Limitations of the DLL and interface are discussed, and opportunities for improving version 2.0 are described.

Safety improvement at nighttime work zones is important because of visibility concerns after dark. The deployment of sequential lights is an innovative method to improve driver recognition of lane closures and work zone tapers. Sequential lights are wireless warning lights that flash in a sequence to delineate clearly the taper at work zones. The effectiveness of sequential lights was investigated with the use of controlled field studies. Traffic parameters were collected at the same field site with and without the deployment of sequential lights. Three surrogate performance measures (the speeds of approaching vehicles, the number of late taper merges, and the locations where vehicles merged into an open lane from a closed lane) were used to determine the impact of sequential lights on safety. The results of this study showed that sequential warning lights had a net positive effect: the warning lights reduced the speeds of approaching vehicles and enhanced driver compliance, and the lights shifted overall merge behavior upstream. Statistically significant decreases of 3.56 km/h (2.21 mph) mean speed and 1.61 km/h (1 mph) 85% speed resulted with sequential lights. The shift in the cumulative speed distributions to the left (i.e., speed decrease) was found to be statistically significant with the Kolmogorov–Smirnov test. With sequential lights, there was a statistically significant increase of 1.47 km/h (0.91 mph) in the speed standard deviation, and the percentage of vehicles that merged earlier increased from 53.49% to 65.36%.

The work zone on the urban road network will affect the surrounding road traffic. To represent the influence area of the work zone, the concept of a subnetwork is proposed in this paper. Delineating a suitable subnetwork quantitatively is a challenging problem. To address this issue, the node synthesized indexes (NSI) are deployed as a variability measure that captures both the change of link flow and origin-destination (OD) demand. The inertia-based stochastic user equilibrium with the elastic demand (ISUEED) model is proposed to accurately provide the data of link flow and OD demand for the network with the work zone. Correspondingly, the data of the network without a work zone can be obtained by the stochastic user equilibrium (SUE) model. According to the value of NSI, the initial range of the subnetwork is determined. Finally, the connectivity and compactness can be guaranteed by the modified L-shell algorithm. To demonstrate the performance of the method, two case studies and sensitivity analyses are conducted based on the Braess network and the local road network in Changchun, China. The proposed method is beneficial to reduce the complexity of the traffic model by substituting the entire network with a subnetwork.

This paper aims to evaluate the effects of work zone configuration, traffic flow, and heavy vehicle percentage on traffic delay at work zones by using a heterogeneous cellular automata (HCA) model. The activity area length and transition area length are two work zone configuration factors taken into account. The average traffic delay per work zone and the average traffic delay per 100m are the two indices used to express traffic delay at work zones. The graphical comparison results show that the transition area length has much bigger effects than the activity area length on traffic delay, especially in the light traffic condition. The function of average traffic delay per work zone is finally formulated that can be used to estimate the marginal effects of the activity area length, transition area length, traffic flow and heavy vehicle percentage.

This paper presents the development of a four-regime speed–flow relationship for highway work zones and the effects of police presence (police) and speed photo enforcement (SPE) on the speed–flow relationship and capacity. The base data were collected when signage typical of that shown in the Manual on Uniform Traffic Control Devices for an Interstate highway work zone with no lane reduction was present. Police and SPE data were collected, respectively, when a police patrol car and an SPE van were added to the typical work zone. From each data set, the step-by-step progression from a three-regime model based on least-squares regression to a four-regime speed–flow curve is presented. The four-regime model comprises four equations: (a) horizontal line for free-flow regime that covered the volume levels up to 900 passenger cars per hour per lane, (b) fourth-degree spline for the upper transition part of the speed–flow curve, (c) another fourth-degree spline for the lower transitions part, and (d) equation in the form of power function for the highly congested part of the speed–flow relationship. The speed–flow curve for the base case had a free-flow speed (FFS) of 61.3 mph and a capacity of 1,850 per car per hour per lane (pcphpl). In the police case, however, the FFS and capacity were reduced by 6.3 mph and 50 pcphpl, respectively. For the SPE case, the FFS and capacity were also reduced by 6.8 mph and 100 pcphpl, respectively. The new curves provided the more accurate speed and work zone capacity estimations required for efficient operation.

Intelligent work zone (IWZ) systems use innovative technologies in real time to mitigate the negative impacts of work zones on the traveling public. The automatic queue detection (AQD) system is one type of IWZ being promoted by the Federal Highway Administration. Several field studies found that AQD systems were successful in reducing average travel speeds which led to a reduction in the number of rear-end crashes and in user costs. It has been shown that well-calibrated microsimulation models are appropriate analysis tools for traditional work zone traffic. To date, there are no tools in the literature that have been developed for AQD operations that have been calibrated and validated with empirical data. This paper aims to fill this gap by providing a comprehensive guideline for calibrating and validating a microsimulation model that can emulate traffic conditions and their impacts on freeway IWZ equipped with AQD systems. Specifically, the methodology includes (1) developing the base work zone model, (2) replicating the AQD warning messages, (3) calibrating the key simulation parameters using three types of data, and (4) validating the resulting simulation model using segment travel times. This comprehensive approach was demonstrated on a Nebraska work zone that was equipped with an AQD system. VISSIM simulation model was used for the underlying tool in the demonstration. The results presented in this paper are useful to both practitioners and scholars who wish to study the impact of the IWZ accurately through microsimulation.