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In the conventional human driving environment, due to poor traffic information transmission and the inability to actively control vehicles, variable speed limits (VSLs) and ramp metering (RM) strategies often fail to achieve the desired results when dealing with the merging zone of an expressway under high traffic demand. To improve traffic efficiency, an integrated control method for traffic flow in the merging area of expressways is proposed by combining connected and autonomous vehicle (CAV) active lane change (LC) technology with traditional VSL and entrance RM strategies. This method uses an upgraded cell transmission model (CTM) to estimate the state of the mainline and ramp input traffic volume and then uses the genetic algorithm (GA) to solve for the optimal combination of the mainline speed limit, number of mainline vehicles changing lanes, and ramp regulation under maximized flow in the merging zone. This integrated control strategy incorporating VSL, LC, and RM (VSL-LC-RM) enables synergistic control of the mainline and ramp traffic entering the merging zone in time-space. Finally, simulation experiments are conducted with the mainline two-lane and on-ramp singlelane expressway merging zone scenarios. The results show that compared with the VSL strategy and the strategy incorporating only VSL and RM (VSL-RM), the proposed VSL-LC-RM strategy can enhance the regulation of traffic flow, improve the flow of merging bottlenecks, and make full use of the road space-time resources. [ABSTRACT FROM AUTHOR]

Variable speed limit (VSL) is becoming recognized as an effective way to improve traffic throughput and road safety. In particular, methods based on traffic state prediction exhibit promising potential to prevent future traffic congestion and collisions. However, field observations indicate that the traffic state prediction model results in nonnegligible error that impacts the next step decision making of VSL. Thus, this paper investigates how to eliminate this prediction error within a VSL environment. In this study, the traffic state prediction model is a second-order traffic flow model named METANET, while the VSL control is model predictive control (MPC) based, and the VSL decision is discrete optimized choice. A simplified version of the switching mode stochastic cell transmission model (SCTM) is integrated with the METANET model to eliminate the prediction error. The performance of the proposed method is assessed using field data from a VSL pilot test in Edmonton, Canada, and is compared with the prediction results of the baseline METANET model during the road test. The results show that during the most congested period the proposed SCTM-METANET model significantly improves the prediction accuracy of regular METANET model. [ABSTRACT FROM AUTHOR]

The effectiveness of speed limit enforcement (SLE) is a critical factor in reducing the global burden of fatalities and injuries due to road crashes. A random-parameter ordered-probit model was developed to explore the relationship between the effectiveness of SLE and different explanatory variables using data from a 2013 World Health Organization global road safety report. An attempt was made to understand the complex interactions between SLE, socio-economic factors, other critical key risk factors and their enforcement levels. Socio-economic status, public policies and road safety legislation and its enforcement were found to be significantly associated with different level(s) of SLE (very low, low, medium and high enforcement levels). Out of seven significant variables, two variables – effectiveness of seatbelt enforcement and road safety audits of new roads – were found to be normally distributed random parameters, suggesting that their effects vary in different countries. The model findings provide preliminary insights into how socio-economic characteristics, road safety policies and traffic laws can be associated with SLE. [ABSTRACT FROM AUTHOR]

In this work, moving synchronized flow patterns (MSP) in empirical city traffic at signals have been observed which was predicted by Kerner (2013, 2014). The single vehicle data has been obtained through aerial observations. Based on this microscopic data, we have found trajectories for all vehicles together with vehicle speeds as functions of time and space. This has allowed us to find empirical MSPs in oversaturated city traffic as well as to perform microscopic analysis, that revealed the following empirical spatiotemporal features of MSPs: (i) MSPs emerge upstream of the queue at the signal and then they can propagate through the complete road section, (ii) merging of several MSPs into a single MSP, (iii) dissolving MSPs and (iv) spontaneous emerging of MSPs faraway upstream of the signal, (v) spontaneous emerging of moving queue within an MSP that is far away upstream of the signal. As a base for this work, we used an unmanned aerial vehicle (UAV) to record videos of inner city traffic situations and supervised tracking methods to gather the vehicle trajectories. [ABSTRACT FROM AUTHOR]

India has shown rapid economic development and this has forced the country to adopt smart traffic management and surveillance process. The intelligent traffic management and surveillance is the basic need for development of smart cities in India. The Intelligent traffic surveillance includes the detection of moving vehicles, estimation of their speed and extracting its registration number. This paper proposes an efficient and novel approach for the detection of moving vehicles as well as estimation of their speeds for detection of any speed limit violation by using a single camera in daylight or properly illuminated environment. The proposed approach detects and tracks the vehicle passing through the surveillance area and maintains the record of vehicles position. The Region of Interest (ROI) of the approach is the dark shaded area formed under the vehicles road clearance area instead of the vehicles. The average detection accuracy achieved by proposed approach is 93.32%. This is on an average 7.54% higher than other existing approaches. The proposed approach uses cropping operation to minimize the scope of any false positive detection on both sides of road. The average tracking accuracy of the proposed approach is about 92.2%. The tracking accuracy achieved by the proposed approach is on an average 2.2% higher than the other leading approaches. The average speed estimation error in proposed approach is +2.2 km/h which is lower than other existing leading approaches. The proposed approach is also time and space efficient over the existing approaches. [ABSTRACT FROM AUTHOR]

In general, the use of superelevation and changes in a road's transverse slope are typically based on the road's design speed to provide safety and comfort for a vehicle driving on a horizontal curve. However, due to the difference between operating and design speeds, there has always been uncertainty in determining the margin of safety using superelevation. This paper discusses the assessment of the safety margins obtained from the application of superelevation in horizontal-curve design. The assessment uses geometric design guides and a reliability index to determine any uncertainties in the design parameters. In addition, adjusted design charts of superelevation values related to the radius of horizontal curves at various levels of probability of noncompliance are provided. The results show that the adjusted superelevation values are generally greater than those derived from current standards. The adjusted design charts can help designers select an appropriate superelevation value for a particular horizontal curve for highways that have geometric constraints. These adjusted charts may also aid designers in predicting the consequences and safety margins associated with the selection of superelevation alternatives required to approve geometric designs that involve violations of the standard requirements due to environmental constraints. [ABSTRACT FROM AUTHOR]

Under certain circumstances, drivers fail to notice changes in electronic speed limits. A video-based study was performed to reveal which countermeasures would improve drivers' ability to detect changes in electronic speed limits. Countermeasures included leaving electronic signs blank prior to a speed limit change and adding motion signals by means of flashing amber lights or a wave. A video representing a motorway was shown repeatedly to 255 participants. They were instructed to press the space bar when detecting a change. The video was viewed 13 times before the speed limit changed. Results showed that leaving signs blank prior to the change instead of displaying speed limits continuously did not alter change detection, whereas flashers and waves eroded detection of the changed speed limit. This suggests that using flashers and waves to attract attention to electronic signs in fact decreases people's ability to process the information contained in the signs. [ABSTRACT FROM AUTHOR]

Education, enforcement and engineering countermeasures are implemented to make road users comply with the traffic rules. Not all the traffic rule violations can be addressed nor countermeasures be implemented at all unsafe locations, at once, due to limited funds. Therefore, this study aims at ranking the traffic rule violations resulting in crashes based on individual ranks, such as 1) frequency (expressed as a function of the number of drivers violating a traffic rule and involved in crashes), 2) crash severity, 3) total crash cost, and, 4) cost severity index, to assist transportation system managers in prioritizing the allocation of funds and improving safety on roads. Crash data gathered for the state of North Carolina was processed and used in this study. Variations in the ranks of traffic rule violations were observed when individual ranking methods are used. As an example, exceeding authorized speed limit and driving under the influence of alcohol are ranked 1st and 2nd based on crash severity while failure to reduce speed and failure to yield the right-of-way are ranked 1st and 2nd based on frequency. To minimize the variations and capture the merits of individual ranking methods, four different composite ranks were computed by combining selected individual ranks. The computed averages and standard deviations of absolute rank differences between composite ranks is lower than those obtained from individual ranks. The weights to combine the selected individual ranks have a marginal effect on the computed averages and standard deviations of absolute rank differences. Combining frequency and crash severity or cost severity index, using equal weights, is recommended for prioritization and allocation of funds. [ABSTRACT FROM AUTHOR]

The article discusses how pavement conditions affect free flow speed (FFS) and the FFS estimation models developed for multilane highways in Jordan. It examines previous studies on field speed and FFS based on the High Capacity Manual (HCM). The research cites the use of the PAVER system and pavement condition index (PCI) as rating tools for selected pavement sections, and confirms the effect of road roughness, speed limit, and standard deviation of vehicle speeds on 85th percentile FFS.

Average speed and speed variance are two characteristics of traffic flow that affect accident rates and severity near work zones. Operationally, work zones account for approximately 24% of the non-recurring delay. A policy for work zone speed limits has to delicately balance the safety and the efficiency impacts. If speeds are set too low, then avoidable congestion and speed violations might result. If speeds are set too high then, again, safety may be compromised. In this paper, results from field studies conducted on three Interstate 70 maintenance short-term work zones in rural Missouri are presented for three different speed limit scenarios: no posted speed limit reduction, 10 mph posted speed limit reduction, and 20 mph posted speed limit reduction. The 85th percentile speeds and standard deviation of speed were found to be 81 and 10 mph; 62 and 8 mph; and 48 and 6 mph, respectively for the three scenarios. The differences in 85th percentile speed and standard deviation of speed among all three scenarios were statistically significant. The per cent of drivers who exceed speed limit by over 10 mph were 15·4, 4·8, and 0·9%, respectively. Thus a reduction in posted speed limit was effective in reducing prevailing speeds and speed variances in short-term work zones in rural Missouri. [ABSTRACT FROM AUTHOR]

Abstract: The misperception of vehicle approach speed is a key contributory factor to road traffic crash involvement. Past research has indicated that individuals use the rate of visual looming to calculate the time to passage (TTP) of a vehicle, and that smaller vehicles loom to a lesser extent than larger vehicles. Despite a disproportionate number of fatal injuries occurring on the road after dark, and a higher than average number of accidents involving automobile drivers violating the right of way of a motorcyclist occurring in low light conditions, there has been very little consideration of the accuracy of TTP for smaller and larger vehicles under low levels of luminance. We investigated drivers’ judgments of motorcycle and car approach speeds across a number of levels of luminance within a virtual city scene, as well as the effectiveness of a tri-headlight formation on motorcycle speed judgments. The accuracy of car approach speed judgments were not affected by changes in lighting conditions, but speed judgments for the solo headlight motorcycle became significantly less accurate as lighting reduced in the early night and night-time conditions. Incorporation of a tri-headlight formation onto the standard motorcycle frame resulted in improved accuracy of approach speed judgments, relative to the solo headlight motorcycle, as ambient light levels reduced. The practical implications of the findings are discussed in terms of road safety and motorcycle design. [Copyright &y& Elsevier]

Abstract: This driving simulator study investigated how mandatory and voluntary ISA might affect a driver''s overtaking decisions on rural roads, by presenting drivers with a variety of overtaking scenarios designed to evaluate both the frequency and safety of the manoeuvres. In half the overtaking scenarios, ISA was active and in the remainder ISA was switched off. A rural road was modelled with a number of 2+1 road sections, thus allowing drivers a protected overtaking opportunity. The results indicate that drivers became less inclined to initiate an overtaking manoeuvre when the mandatory ISA was active and this was particularly so when the overtaking opportunity was short. In addition to this, when ISA was activated drivers were more likely to have to abandon an overtaking, presumably due to running out of road. They also spent more time in the critical hatched area—a potentially unsafe behaviour. The quality of the overtaking manoeuvre was also affected when mandatory ISA was active, with drivers pulling out and cutting back in more sharply. In contrast, when driving with a voluntary ISA, overtaking behaviour remained mostly unchanged: drivers disengaged the function in approximately 70% of overtaking scenarios. The results of this study suggest that mandatory ISA could affect the safety of overtaking manoeuvres unless coupled with an adaptation period or other driver support functions that support safe overtaking. [Copyright &y& Elsevier]

Road vehicles equipped with appropriate measurement equipment, computing facilities, data storage and data communication capabilities can be considered valuable data sources for the description and quantitative characterisation of road traffic. The data obtained from these vehicles provide valuable direct and indirect information pertaining to traffic states and various aspects of traffic safety in respect of the analysed road network. In this study, trucks' abrupt braking events, detected by the trucks' on-board safety protection units, were analysed. The road locations of the detected abrupt braking events can be characterised by a number of features ranging from the specific traffic regulations (e.g., speed limits) in force to the socio-cultural environment of the location. The abrupt braking data evidence was used for identification and description of non-trivial interactions of drivers, trucks and roads. Some of the more interesting results and conclusions of the experiments are reported herein. [ABSTRACT FROM AUTHOR]

Sometimes experts, decisionmakers, and analysts are confronted with policy problems that involve deep uncertainty. Such policy problems occur when (1) the future is not known well enough to predict future changes to the system, (2) there is not enough knowledge regarding the appropriate model to use to estimate the outcomes, and/or (3) there is not enough knowledge regarding the weights stakeholders currently assign to the various criteria or will assign in the future. This paper presents an MCDA approach developed to deal with conditions of deep uncertainty, which is called Exploratory Multi-Criteria Decision Analysis (EMCDA). EMCDA is based on exploratory modelling, which is a modelling approach that allows policy analysts to explore multiple hypotheses about the future world (using different consequence models, different scenarios, and different weights). An example of a policy problem that can benefit from this methodology is decision making on innovations for improving traffic safety. In order to improve traffic safety, much is expected from Intelligent Speed Adaptation (ISA), an in-vehicle system that supports the driver in keeping an appropriate speed. However, different MCDA studies on ISA give different results in terms of the estimates of real-world safety benefits of ISA and the willingness of stakeholders (e.g. the automotive industry) to supply ISA. The application of EMCDA to the implementation of ISA shows that it is possible to perform an MCDA in situations of deep uncertainty. A full analysis taking into account the complete uncertainty space shows that the best policy is to make mandatory an ISA system for young drivers (less than 24 years of age) that restricts them from driving faster than the speed limit. Based on different assumptions, the analysis also shows that ISA policies should not target older drivers. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to explore the interrelationship between driver distraction and characteristics of driver behavior associated with reduced highway traffic efficiency. Background: Research on the three-phase traffic theory and on behavioral driving suggests that a number of characteristics associated with efficient traffic flow may be affected by driver distraction. Previous studies have been limited, however, by the fact that researchers typically do not allow participants to change lanes, nor do they account for the impact of varying traffic states on driving performance. Methods: Participants drove in three simulated environments with differing traffic congestion while both using and not using a cell phone. Instructed only to obey the speed limit, participants were allowed to vary driving behaviors, such as those involving forward following distance, speed, and lane-changing frequency. Results: Both driver distraction and traffic congestion were found to significantly affect lane change frequency, mean speed, and the likelihood of remaining behind a slower-moving lead vehicle. Conclusions: This research suggests that the behavioral profile of "cell phone drivers," which is often described as compensatory, may have far-reaching and unexpected consequences for traffic efficiency. Application: By considering the dynamic interplay between characteristics of traffic flow and driver behavior, this research may inform both public policy regarding in-vehicle cell phone use and future investigations of driving behavior. [ABSTRACT FROM AUTHOR]

The efficacy of a theory of planned behaviour (TPB)-based intervention to promote drivers' compliance with speed limits was tested. Participants (N = 300) were randomly assigned to an experimental condition, and received persuasive messages designed to change beliefs as specified in the TPB, or a control condition. Baseline and follow-up (1 month post-baseline) measures of TPB variables and behaviour were collected using postal questionnaires. Results showed that the intervention had a significant effect on one control belief, and significantly increased perceived behavioural control and reported behaviour. Mediation analyses confirmed that the control belief change generated the perceived behavioural control change and that the perceived behavioural control change generated the behaviour change. Implications for promoting road safety are discussed. [ABSTRACT FROM AUTHOR]

Robust road-boundary extraction/tracking is one of the main problems in autonomous roadway navigation. Although the road boundary can be defined by various means including lane markings, curbs, and borders of vegetation, this paper focuses on road-boundary tracking using curbs. A vehicle-mounted (downward tilted) 2-D laser-measurement system is utilized to detect the curbs. The tracking problem is difficult because both the vehicle is moving and the target is disappearing, reappearing, and maneuvering in clutter. The interacting-multiple-model probabilistic-data-association filter (IMMPDAF) is proposed to solve the problems after detailed analysis. Track initiation, confirmation, and deletion are performed using the sequential-probability-ratio test. Extensive simulations followed by experiments in a campus environment show that the road-boundary tracking utilizing curbs is possible and robust through IMMPDAF. [ABSTRACT FROM AUTHOR]

In this paper, an iterative learning approach for the freeway density control under ramp metering and speed regulation is developed in a macroscopic level traffic environment. Rigorous analyses show that the proposed learning control schemes guarantee the asymptotic convergence of the traffic density to the desired one. The two major features of the learning-based density control are 1) less prior modeling knowledge required in the control system design and 2) the ability to reject exogenous traffic perturbations. The control schemes are applied to a freeway model, and simulation results confirm the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

The primary purpose of our highway system is mobility, not safety. If it were the latter, we would set speed limits much lower. A 20 mph speed limit, with governors (speed limiting devices) on all motor vehicles to prevent exceeding that speed, would certainly lower highway casualties. Of course, no one would consider such a measure. Clearly, we tacitly agree to accept a certain level of carnage in order to use the highways in ways we value. At the present time in the US, this tacit agreement says that it is acceptable to sacrifice between 40,000 and 42,000 lives annually. The primary purpose of our highway system is mobility, not safety. If it were the latter, we would set speed limits much lower. A 20 mph speed limit, with governors (speed limiting devices) on all motor vehicles to prevent exceeding that speed, would certainly lower highway casualties. Of course, no one would consider such a measure. Clearly, we tacitly agree to accept a certain level of carnage in order to use the highways in ways we value. At the present time in the US, this tacit agreement says that it is acceptable to sacrifice between 40,000 and 42,000 lives annually. By 1980, excessive regulation of railroads and competition from other modes of transportation, such as trucks and barges, had nearly killed the rail industry. The federal government tightly regulated the rates railroads could charge shippers and the railroads' ability to shed unprofitable lines. The Staggers Rail Act of 1980 ("Staggers Act") eliminated a regulatory scheme in which a government agency set rail rates that uniformly applied to shippers in favor of rates set through negotiations between a railroad and a shipper. The legislation was enacted to unleash the industry from this regulatory regime. Since 1980, the financial health of the rail industry has improved, but most railroads remain revenue inadequate—they do not earn enough revenue to maintain their current infrastructure. Even though rail traffic has grown, the rates railroads charge shippers have generally declined over the last two decades. Railroads, therefore, cannot afford to expand their infrastructure to keep pace with traffic growth because building and maintaining a rail network is very expensive. In the future, railroads will have to raise their rates, which may drive less profitable traffic to the nation's highways and waterways, or invest in infrastructure so they can handle more traffic. Government policy can help the railroads while simultaneously avoiding additional congestion on our highways and waterways, and reducing pollution, fuel consumption, and damage to the highways. The United States' railroad policy could give railroads more resources to expand their infrastructure and assure that railroads have the proper economic incentives to make the investment in infrastructure necessary to meet the demand for their services. That policy must also encourage creative financing and public-private partnerships to the same end. Finally, policies to promote investment in rail infrastructure must not result in a quid pro quo of increased regulation of the industry. Such regulation would likely negate the benefits of encouraging infrastructure investment by driving away private investment, and the industry would need more public money to survive. [ABSTRACT FROM AUTHOR]

The article focuses on various articles published in Journal of the Transportation Research Forum, related to transportation safety. In the article "New Speed Limits on Kansas Highways: Impact on Crashes and Fatalities," by Yacoub Najjar, Eugene Russell, Robert Stokes, and Ghassan Abu-Lebdeh examine the impact of recent changes in speed limits on Kansas highways. The authors note that the National Maximum Speed Limit of 55 mph was eliminated in November 1995, thus returning the authority of establishing speed limits to the states. By the end of 1996 a total of 32 states had raised speed limits on their highways. In Kansas, speed limits of most rural, separated, multilane highways were raised to 70 mph, while on most urban interstate and two-lane rural highways the limit was increased to 65 mph. The main objective of the paper is to determine whether statistically significant changes have occurred in accident related indices such as crash, fatal crash, and fatality rates after the Kansas speed limits were increased. In the article "Seat Belt Use Compliance in Kansas," by Deogratias Eustace and Teresa Bartel examine trends in Kansas seat belt use.