Access Management Theories and Practices

The Transportation Research Board Access Management Committee initiated an effort to promote international understanding and integration of roadway access management into the transportation planning and design decisions of nations around the world. This paper summarizes findings of the first step of this effort, which is to identify the international state of the practice. Issues addressed include historical context, legal framework, processes for addressing roadway function, access control and enforcement schemes, associated land use and development regulation processes, pertinent policies and standards, transportation modes addressed, and related issues. This paper presents selected highlights from the following countries that responded to the survey: United States (U.S.), South Africa, China, South Korea, Greece, Germany, Poland, and the United Kingdom (U.K.).

Raised medians offer a departure from more traditional two-way left turn lanes typically built on collector and arterial streets and can offer advantages in terms of safety, capacity, and aesthetics. At the same time, individual business owners often oppose raised medians due to fear of business loss. This paper summarizes research on the effects of raised medians on retail sales in Utah before and after the installation of raised medians. Sales analysis was also performed for corresponding control corridors in which a similar roadway project was completed that did not include the installation of a raised median. For all of the corridors in which raised medians were constructed, there was an increase in corridor-area retail sales and sales per square foot. Analysis showed that in every case there was no evidence of a negative impact on corridor sales due to the raised median installation. A business impact survey was administrated to qualitatively evaluate the perceived impacts of each road project in front of individual businesses. Business owners on corridors, where the project included the installation of a raised median, typically perceived the actual results of the project more negatively than corridors, where the project did not install a raised median.

In this paper, characteristics of access control on Polish national two lane roads, rural and urban, and its evaluation on traffic performance is presented. In order to demonstrate the impact of access control and traffic performance, quantification of factors associated with the road and its surroundings was carried out. The study was based on empirical research and on developed regression models of speed. These models were used to evaluate the expected value of vehicle speeds on sections with different levels of access control. The study indicated a significant effect of the lack of access control on traffic performance. Conclusions based on the regression models were used to emphasize the most important issues caused by the absence of proper access management on existing roads. Moreover, proposals for possible methods to solve indicated problems were presented. As a result, the recommendations were formulated in relation to the following countermeasures, e.g., infrastructure investments, traffic, and access management, whose main goal is to improve traffic performance on Polish roads.

Earthquake is one of the serious geological disasters in China, it would cause varying degrees of damage to road lifeline. Due to the difficulty of quickly getting the damage information of road lifeline after earthquake, it has a great impact on the rescue work. The paper provided the seismic damage grades of subgrade, bridge and tunnel according to seismic damage type, and the influence on road traffic function. Then, the relationship between seismic intensity and road damage was analyzed. The rapid diagnostic model of road lifeline seismic damage based on seismic intensity was constructed from the following aspects: division of assessment unit, construction of seismic damage index set, determination of weight set, and model validation. The model can improve the emergency rescue efficiency through rapidly forecast the highway damage risk.

Access management can be generally defined as the coordinated planning, regulation, and design of access between roadways and adjacent land. The practice of access management has steadily evolved over the past century as an important element of the U.S. transportation policy. Since the 1980s, dramatic advances in access management have taken place along arterial roads, particularly in suburban settings. Colorado established the first statewide access management program in the U.S. (1980), followed by statewide codes or increased efforts in several other states. The American Association of State Highway Transportation Officials Policy on Geometric Design of Highways and Streets expanded its treatment of access management in 2001 and 2003, the first U.S. Access Management Manual was published by the Transportation Research Board. The documented safety and operational benefits of access management techniques have also led to policies in several other nations. These advancements continue to raise awareness of the need to manage traffic conflicts through functionally designed roadway networks with varying levels of access and mobility. This presentation explores the U.S. concept of access management, including recent developments, and addresses the importance of access management to the quality and safety of every nation’s transportation system.

This paper seeks to demonstrate the importance of expanding the orientation of access management of the major roadway system beyond the goals of maintaining high-speed through movement. Speeds can be managed without increasing congestion. The paper also addresses how access management and design can better relate to pedestrians, bicyclists, and public transportation. The profession must be more aware of the land use and community context, where access management techniques are being applied. Context changes over time and it also changes by location. Therefore, the same approach will not be appropriate on all segments of a roadway or in all countries or regions. A change in the focus of access management with regard to context is consistent with recent trends in transportation and urban planning.

During the mid-nineteen nineties, the need to properly define a safe and consistent approach for dealing with property access applications was identified. To this end, a unique approach was adopted in an attempt to find a balance between the demand for access to encourage development and the need to protect the rights of the wider community for sustainable transportation, more particularly road infrastructure development, while at the same time ensuring adequate mobility in support of accessibility to economic opportunities. This resulted in the production of a document “Road Access Guidelines”. This document is still in use. During 2012, it was decided to produce a new guideline on access management, taking into account the development of the science of access management around the world and the changed environment within the region during the ensuing years. This new document serves to set out guidance for the overall management of access for people and goods from the road network to adjacent land uses and to determine the type and overall spacing of such accesses so as to minimize the disruptive effect of access conflicts on the operating performance of all users of the relevant elements of the road network.

Access management involves control, planning, and coordination of access along roadways to provide safe and efficient operation of transportation networks. According to existing literature, reducing conflict points and improving traffic safety are the main goals of access management techniques. Increase in traffic volumes and rapid growth of roadway networks have made these efficient techniques as a crucial part of roadway planning and design process. Some of the access management techniques employed in the recently published Highway Safety Manual (HSM) include: median treatments, traffic signal spacing, auxiliary lanes, corner clearances, driveways, U-turns as alternatives to direct left-turns, and frontage roads. Moreover, the Crash Modification Factors (CMFs) of these techniques, as estimators of the actual safety effect of countermeasures, are utilized in the HSM predictive methods to approximate the potential changes in crash frequency and severity after treatment implementation. The results of this study provide transportation agencies, practitioners, and decision-makers with a better understanding of how the HSM methods quantify the safety effects of access management techniques on different roadways. This is accomplished by providing output in the form of tabulated ranking of the impact of access management parameters for three roadway facilities defined in the HSM using the graphical method of sensitivity analysis.

Traffic safety is one of the principal factors considered by whom accessing the traffic system, such as drivers and pedestrian. Intending to reduce the probability of traffic accidents in the process of access, this study elucidates a new prospective on an accident analysis from a view of considering various accident-related factors as a system, including three major parts as road environment, traffic facilities, and vehicles. The instability of traffic system indicates the accident potential in certain system. By investigating the correlation between accident and relative factors, describing the system instability and comparing different systems, it is accessible to find out the cause of traffic accidents in urban road network of third-tier cities in China. After analyzing accident statistics from 2006 to 2010 in Urumqi, China, six types of urban roadways accidents are selected as a dependent variable, meanwhile, independent variables include road environment, traffic facilities, and vehicle types. By analyzing the impact degree of each factor on single crash type based on binary logistic model, the weight of each factor in the system is decided. Then, a multimodal logistic model is built to describe the accident probability distribution in different systems with different combinations of factors. Based on the result of binary and multinomial logistic regression, it is approachable to reach an understanding of system instability and analysis the cause of traffic accidents in urban traffic systems in third-tier cities of developing country.

As a kind of environmentally friendly transport tool, mopeds are popular among clerks and students. However, mopeds violation behaviors become a serious threat to the safety of vehicles and pedestrians at mixed traffic intersections. This study investigates the nature of violations and observed behavior and characteristics of moped riders from video data and traffic count data collected. One intersection in Wuxi was selected to obtain the videos of peak hours. Results suggested that the violation rate of moped is 35% exclusive of improper behaviors. Occupying vehicle lane is the most common violation behavior, which has a violation rate of 0.16. According the result and the video, some characteristics of moped riders were summarized, such as group psychology, willing to overtake, and so on. Therefore, enhancement of traffic facilities and traffic management, and traffic safety education are necessary in order to reduce such violation behavior, to improve traffic safety in mixed traffic intersection.

From the point of expressway operating safety and effectiveness, expressway operating environment is defined here as the system composing road, traffic, climate, and humanistic environment. All traffic activities would be operated inside the environmental space. Therefore, accurate description and reasonable evaluation of operating environment and operation safety seem to be very important. Currently, there is lack of a set of scientific and operable technical indexes to describe and evaluate expressway operating environment for safety design and operation. According to the recent research results, a set of evaluation indexes of expressway operating environment for safety design and operation has been proposed in this paper, where the expressway geometric alignment, road and traffic infrastructures environment, and the traffic flow operation status are considered. This index system could be used as a tool for safety design, safety evaluation, and operation management.

Junctions are basic joints of road network and their models affect traffic operation and safety greatly. There are quite number of Y shaped junctions at the highway. The existence of such abnormal junctions lowers operation efficiency and triggers traffic accidents. In the rebuilding constructions, T shaped junctions may be new builds but often are converted from Y shaped junctions. For more engineering applications, there is a need to estimate the safety effects of conversions. Several studies have estimated reductions in crashes and severity; however, these results pertain mainly to conversions from Y junctions without signal control. Results for conversions from signalized Y junctions have been less conclusive. Our study aimed to fill this void by estimating the safety performance of converting signalized Y shaped junctions to signalized T shaped junctions. Several cities in Jiangsu province along the national highway G205 helped to identify in the recent past. The empirical Bayes method was used to estimate the safety effects of conversations. The results indicated a safety benefit for converting signalized Y shaped junctions to T shaped junctions. There were reductions in both total and injury crashes, with a larger benefit for non-vehicle injury crashes. Further analysis indicated that the safety benefit of T shaped junctions for total crashes decreased as traffic volumes increase, a result that suggests the need for the development of a crash modification function (CMF), a task for which more data would be required.

Based on numerous research works on road traffic safety, the space curvature index of expressway alignments was developed considering road alignment space geometric properties and its impact on traffic accident. This index was modified to reflect the influence of the curvature on highway operating speed. The road safety performance and operating speed of several expressways were investigated and the regression relationship between single-vehicle accident rate and space curvature index of highway alignments was studied. So that the space curvature index of highway alignments could be used as a prediction factor of traffic accident in highway alignments during highway alignment safety design and road safety analysis.

Access of relief road links traffic with facilities on the roadside that can be terminal of drivers. Nevertheless, the intervals between accesses are often not taken into consideration, or only in very rough ways. This paper aims at demonstrating a modeling approach to determine appropriate access intervals, which is based on car following theory. Vehicles always change lane from the relief road into the main stream at a quite lower speed, as a conflict to the main stream, which would lead to a temporary decline to traffic capacity. Utilizing the model of car following and the design capacity of freeway correspondingly, we find the expected maximum length it will affect. The proposed length is assumed not to reach the next access in order to avoid negative interaction, and therefore determine it as the minimum interval between accesses. We expect that this study can make available appropriate relief road access intervals.

In China, with the auxiliary lane construction acting as an important means of access control management, more and more auxiliary lanes are constructed on the high-grade roads, but the opening size of those auxiliary lanes lacks definite rules and theoretical basis. In this paper, the characteristics of driving behaviors of entering and exiting the auxiliary lanes are considered, and a relative kinematics model is established on the basis of lane changing theory. The Minim Opening Safe Spacing (MOSS) is presented and acts as the safety index of the opening at certain speed. A final driving simulation test proves the good applicability of the model.

Freeway is the type of facility that enjoys the highest level of access control. It serves the main purpose of mobility instead of accessibility. However, due to the ever-increasing travel demand and challenges to building new freeways, the existing freeway facilities are retrofitted with a full range of system management strategies, such as entrance ramp metering and managed lanes, and the consideration of non-motorized travel demand. The implementation of these strategies presented a unique set of access management issues, such as new geometric design standards, and project development policies and procedures. A general introduction of the freeway access management practices in California is presented in this paper, together with the key traffic engineering and design considerations related to ramp metering, managed lanes, and consideration of non-motorized travel demand.

Through observation and data analysis of the eight-lane highway deceleration lane existing in China, it finds that large vehicles have lower speed better driving regularity than small ones, and that the deceleration lane can meet the demands of large vehicles. In this study, it focuses on the small vehicles and combines running speed, average speed, and designing speed to study, in which it considers the impact of large vehicles. Considering the way of deceleration lane calculation based on quadratic deceleration, it divides the deceleration lane into three sections which are triangular transition section, the first deceleration section and the second deceleration section, according to the deceleration process and characteristics in each one, and study the related parameters. At last, it proposes the deceleration lane calculation model and the corresponding recommended value.

During the last decade, urban interchange ramps were widely constructed in China, which also associated with a rapid increasing number of traffic accidents. Among various causal factors to traffic accidents, the environment factor, crosswind, has been proved to be correlated with occurrence of accidents happened on urban interchange ramp. In order to improve the traffic safety for urban interchange ramp, the impacts of crosswind on traffic safety were investigated in this paper. Using hot-wire anemometer, it is demonstrated that the wind speed at traffic accident hot spots is much bigger than that of the nearby weather station at the same time. Then several computational fluid dynamics (CFD) simulation models were developed to illustrate the impacts of crosswind on traffic safety. The results indicate that driving around the windward side on a ramp is the most dangerous situation compared to the other scenarios and the aerodynamic force of automobile can change significantly during overtaking process.

This paper evaluates the safety of lane changing behavior in freeway off-ramp section. Firstly, we discussed the relationship among lateral force coefficient, lateral stability of vehicles, and drivers’ physiological status. Then, we conducted the analysis of vehicle and drivers by establishing the models of the steering angle and lateral force coefficient. Based on this, the distribution chart of lateral force coefficient in different alignment conditions was obtained. Lastly, we proposed the safe steering angles of front wheel for different alignment conditions. The results can reduce the accident rates on off-ramp sections on freeways.

Since the opening of the first Diverging Diamond Interchange (DDI) in the U.S. in June 2009, 34 DDIs have been completed as of March 2014. At least 40 more DDIs are being planned/designed/constructed. The sheer number of DDI projects indicates this innovative design is gaining wide acceptance. Field results demonstrate that this design is much more cost effective than the conventional improvement designs. By converting the 3-phase signal at traditional diamonds into 2-phase, DDI provides more effective green time for moving traffic. Most DDIs constructed to date are near large business, retail, and/or medical centers; and the intersections adjacent to DDI crossovers often have high traffic demands and require 6 or more phases and longer cycle length to serve the demands from conflicting movements. Such condition limits the DDI’s capacity utilization. This study explored three approaches to reduce the cycle length at nearby signals—relaxed Bowtie, Superstreet, and Quadrant Roadway intersections. They can all convert the adjacent intersections into 2-phase operation and enable the DDI to operate more efficiently. The ideas were tested in a simulated environment at a proposed DDI in Anchorage, Alaska. The simulation results indicate level-of-service at nearby intersections may be improved from D/E to A/B.

In all kinds of safety measures, access management techniques have been proved the most successful in improving the safety and efficiency of arterial roads. The purposes of this research, therefore, were to objectively and comprehensively evaluate the highway safety from the aspect of access management. In this paper, we propose a three-layered (micro-meso-macro) framework that provides safety evaluation at different levels of details. At the macro level, system-wide goals are achieved, we considered highway safety with road functions and land-use; on meso level, safety is concerned with access distance and access types; and at macro-level, we made the consideration of safety protection designs at access points. We believe that the combination of access management at each of the levels may lead to a more efficient and sustainable use of the highway infrastructure.

The purpose of this paper is to relate a planning procedure for the systematic retrofit of a four lane suburban expressway to a six lane urban freeway. The retrofit is likely years away and will require a number of projects over multiple funding programs. To develop an implementation-ready corridor access management plan, it is necessary to balance priorities for land-use (intensity, livability, walkability, and sustainability) and desires for public safety and accessibility on the public roadway system (safety and capacity constraint). The desired result is a plan that will systematically retrofit a suburban expressway into an urban freeway through a combination of access management, corridor preservation, and development coordination. Land-uses and transportation networks exist in a demand/supply relationship just as any economic system, and a general equilibrium is sought throughout the years required for full retrofit. Negative economic and environmental impacts will compound over time, and the public safety will be compromised, if inappropriate access connections and intersection controls are allowed. An area-wide access management plan was developed beginning with an understanding of future traffic generation/distribution characteristics and the capacity constraint requirements of the various regulatory partners. A VISSIM model was developed with the capacity constraints and future traffic demands were added. Points of interchange with the freeway system were identified, and then “nodes” of connection for the supporting street network were added. With a transportation system framework in place, a land-use plan was developed. Development characteristics were identified that will fully leverage the capacity of the planned transportation network. The foundation of an implementation plan was developed to allow for cooperation and coordination between multiple levels of government. Execution of this plan will provide for improved economic and environmental sustainability and public safety.

Past studies indicated that interchange configurations, access control, and geometric design are related to Wrong-Way Driving (WWD) and minor ramp geometric changes can be effective in reducing the number of wrong-way entries onto freeways. In this paper, access management techniques and geometric elements, which are capable of discouraging wrong-way maneuvers, are identified and discussed. Additionally, every aspect of these elements and their relationship to WWD is investigated. These geometric elements include interchange types, exit ramp terminals, frontage roads, raised medians, channelizing islands, and control radius. The aforementioned elements should be given a special consideration during the design stage of interchanges and intersections.

This paper presents the result of a study carried out to identify vehicle queue effects of driveway geometry based on statistical analysis of field survey data. The study is necessary to help transportation engineers apply highway access control more efficiently to achieve its full benefits such as diminished queue lengths in main roads as well as in driveways. We applied the multiple regression analysis to establish evidence based on vehicle queues and driveway geometric features. Our research showed that vehicle queues actually vary closely with driveway geometric conditions and that the presence of the speed bump and the crosswalk are the most important factors for increasing vehicle queue lengths. The research findings will contribute to our increased understanding of proper driveway designs when highway access control is the main research interest.

This paper studies the performance of single-lane roundabouts with a direct driveway access road, one lane driveway right-out movements only, to allow facility (land parcel) driveway volumes to access directly at a roundabout. VISSIM micro-simulation assessment considers experimental origin-destination (O-D) balanced flow scenarios with three different driveway volumes (low, moderate, high, and compared to no driveway) and with and without slip lane scenarios (no slip lane, one slip lane, and two slip lanes). Simulated right-turning traffic volumes range from 50 to 500 vehicles per hour. Experiment results indicate that average delay of a roundabout is sensitive to changing driveway’s volumes. As expected, results indicate a direct access driveway, which increases the roundabout vehicle average traffic delay. At high driveway’s volumes level, the total average roundabout delay was increased by 50% at a moderate vehicle traffic level and by 71% at a high vehicle traffic level, before oversaturation. The total average driveway traffic delay was also increased by 8% at a moderate traffic level and by 12% at a high traffic level. Finally, this study also suggests that having more than one slip lane, at different roundabout approaches, reliefs total roundabout average delay, provides an efficient direct roadway driveway access, and enhances access management.

Integral to the application of Access Management is the road classification system. Road classification in urban areas boils down to defining the higher order mobility routes (Classes 1 to 3) and then managing access provision to be commensurate with the classification. These higher order routes tend to define the urban form, as they have larger road reserves, more lanes and can end up as some form of barrier. They are also crucial for the functioning of cities (provision of mobility) as they are carrying the highest numbers of vehicles and consequently the highest vehicle-kilometre of travel.One objective of this paper is to evaluate the spacing of these higher order roads in some real world cities, in view of the ideal spacing guidelines. The existing density of higher order routes in Cape Town (South Africa) has been determined and compared (on strategic level) with four major cities in other parts of the world (Berlin, Melbourne, Dallas, and Shanghai). A further objective is to investigate the consequences of access spacing guidelines on real world situations. Issues with respect to real situations experienced in Cape Town are illustrated and compared with local and international standards. An approach to implementing the ideal standards is suggested, also in view of the guidance provided in the access management manual.

In order to improve the traffic safety and efficiency of new access roads in old city reconstruction, it is necessary to do research on site selection, layout design, and management of access road. By integrated analysis of multi-level road traffic operation, this paper determines the service level of access road using equivalent traffic capacity replacing intersection capacity as the representative value of road traffic capacity, and in according to the relationship of equivalent capacity and intersection spacing, back calculation of the optional areas of access roads is, which replaces the design method aimed at meeting the demands of the functional areas of intersection. Finally, according to this design idea, we use the road traffic simulation system to simulate the design of access road in the reconstruction of Qi county HeBi city Henan province. The results show that this method satisfies the road network service level and maximizes the system traffic capacity on the basis of traffic safety.

The paper is based on work undertaken for the 2014 edition of the “access management guidelines,” developed for the Western Cape Provincial Government of South Africa, and which will replace the “road access guidelines” published by that Government in 2001. The aspect covered in the paper deals with the spacings that should be allowed between different categories of unsignalised intersections along different categories of urban at-grade roads. Firstly, the paper examines the candidate criteria for determining spacings of unsignalised public roads and private driveways, and then presents the conclusions reached on the appropriate criterion for each combination. The rationale for selecting criteria is based on one of the two presumptions: the task facing the driver negotiating the road and who must undertake processes of decision-making and actions when approaching an intersection ahead (i.e., operational requirements); or alternatively, the manoeuvre required of a driver to avoid a collision (i.e., safety requirements). The application of these principles is used to establish appropriate spacing distances along the through road, depending on the classification of the through road and the type of intersection or driveway intersecting with the through road.

Currently, the study on access design has not yet conducted widely in large cities such as Beijing. As a result, there is no specification or criterion to dictate the layout and design of driveways connecting to roadways. Generally, these driveways are closely located to the signalized intersection. The egress and ingress of vehicles will greatly impact the operation of traffic at the intersection. In addition, this type of design brings about serious safety problems. The objective of this study is to determine the minimum spacing between access and signalized intersection of Beijing based on corner clearance technology. As is known, corner clearance technology is one of the access management strategy. By analyzing the constraints on the corner clearance of the intersection, the influencing factors are determined. On this basis, a minimum spacing model between the access and the intersection is established in the paper. In order to analyze the influencing factors on corner clearance of urban major roadways, the simulation model is used. The delay is regarded as an evaluation index. The simulation-based minimum corner clearance is determined. The result of this study can help traffic engineers to make sensible decision on the layout and design of accesses near the signalized intersections of Beijing.

In the calculation of urban signalized intersection capacity, the effects of road and traffic conditions, which includes on-street parking maneuver rate, local bus stopping rate but not the access. Traffic that drives in and out of the accesses have a negative impact on both the smoothness of the main road traffic and the capacity of the downstream intersection. An analysis of how the assess traffic affects the downstream signalized intersection shows that the merging or passing through of the access traffic leads to green time loss of the intersection. The green time loss can be expressed by the merging time of the access. A regression analysis reveals that the merging time of the passing through traffic have a correlation with the distribution of the main road, but not strong. Then, the capacity calculation model, which consider both the access traffic and the main road traffic arriving is formed. The model shows that accesses lead to the capacity loss of the signalized intersection. At last, the result of the model is demonstrated with a numerical example.