Interchange Ramp Research Articles

Research on the Running Speed Prediction Model of Interchange Ramp

Ramp is an important part of the interchange. The ramp design concept based on the running speed is a new design idea of the highway and interchange. By analysis of the influence factors of the interchange ramp running speed, this paper formulates the orthogonal experiment, and collects 14 ramps, in total of 147 groups of the running speed as the samples, and then analyzes the characteristics of the running speed of the vehicles on interchange ramp. According to the change trend of the running speed, the ramp is divided into three sections: deceleration section, uniform section, acceleration section. This paper mainly analyzes the relationship between the interchange ramp running speed of the three sections and the influence factors; and then this paper builds the interchange ramp running speed prediction model of the three sections. At last, correlation test will be validated, and verify the applicability of the model.

Landslide Evolution Rule of Cut Slopes in Expansive Soils

Expansive soils in cut slopes are prone to sliding for a period of time after excavation. They are commonly found during construction in expansive soil subgrade. Their sliding is not directly affected by the height and ratio of the slope. To understand the evolution of their deformation and the consequences of failure to implement effective engineering treatment, the finite difference procedure FLAC is used to analyze the regularity of the excavation process of expansive soil slopes and obtain the displacement, stress, and strain. The safety factor for slope cutting calculated by using the strength reduction method decreases as the slope depth increases, but is still stable after the complication of excavation. In addition, the thermodynamics module of the finite difference procedure FLAC is used to simulate the humidity field of the atmospheric effects for the expansive soil slope and to obtain the variability of the displacements, stresses, and strains of the cut slope after wetting and drying cycles. The numerical simulation results are basically in accordance with field observation results during and after the construction of cut slopes in the Sitang interchange ramp of the Bailong expressway in Guangxi Zhuang Autonomous Region, China. The four stages of evolution of expansive soil cutting slopes are summarized. It is proposed that flexible supporting structure technology should be used.

Assessing factors causing severe injuries in crashes of high-deck buses in long-distance driving on freeways

High-deck buses that have a higher center of gravity traveling at an excessive speed have a higher likelihood of causing serious and fatal accidents when drivers lose control of the vehicle. In addition, drivers who suffer from fatigue in long-distance driving increase the likelihood of serious accident. This paper examines the effects of risk factors contributing to severe crashes associated with high-deck buses used for long-distance driving on freeways. An ordered logit and latent class models are used to examine significant factors on the severity of injuries in crashes related to high-deck buses. Driver fatigue, drivers or passengers not wearing a seat belt, reckless driving, drunk driving, crashes occurred between midnight and dawn, and crashes occurred at interchange ramps were found to significantly affect the severity of injuries in crashes involving high-deck buses. Safety policies to prevent severe injuries in crashes involving high deck buses used for long-distance runs on freeways include: (1) restricting drivers from exceeding the limit of daily driving hours and mandating sufficient rest breaks; (2) installing an automatic sleep-warning device in the vehicle; (3) drivers with obstructive sleep apnea syndrome or sleep disorders should be tested and treated before they are allowed to perform long hours of driving tasks; (4) educating the public or even amending the seatbelt legislation to require all passengers to wear a seat belt and thus reduce the chance of ejection from a high-deck bus and prevent serious injuries in a crash while traveling at a higher speed on freeways.

Study on Control Design of Interchange Entrance Congestion Zone

Interchange entrance area is the key point which affects the overall operational reliability of an Interchange. In order to alleviate the crowded ramp merging area, improve the overall reliability of the interchange and improve traffic safety, when traffic demand increases to a certain extent, traffic control strategies should be used. According of the characteristics of the interchange ramp entrance area, the control strategy of interchange and the mainline which affect the reliability of high-speed road network most has been researched. Analyzing the geometric and traffic characteristics of the ramp merging area, different control strategies on the ramp and the mainline are proposed, that is ramp access control strategy and the main line lane running constraint strategy.

Study on the Static and Dynamic Load Test of Ramp Bridge

Ramp bridges are usually curved girder bridges, and show unique mechanical characteristics under live load. On the basis of an interchange ramp bridge static and dynamic load test in a radius of 230m, the bridges stress, deflection and dynamic characteristics were analyzed and the bearing capacity was evaluated.

Bridge Structure Performance Evaluation Based on Dynamic Load Test

Static load test was carried out on Hengshui interchange ramp bridge of Lin-Chang expressway. The superstructure of the bridge is cast-in-place prestressed concrete continuous box-girder. The actual service state of the bridge is analyzed by the comparison of experimental and calculation results. The study provides the initial technical files and the basis of acceptance, operation, maintenance and management for the bridge.

Field Data for Evaluating 2010 Highway Capacity Manual Operational Analysis Methodology for Interchange Ramp Terminals

Interchange ramp terminals provide connections between various highway facilities (freeway–arterial, arterial–arterial, freeway–freeway, etc.), so their efficient operation is essential. NCHRP Project 3–60 developed analysis methods for evaluating the operational performance of signalized interchange ramp terminals. Those methods were based primarily on simulated data. Further research used collected field data to evaluate the interchange analysis methodology developed under NCHRP Project 3–60 to identify application limitations and to suggest improvements. Data were collected at eight sites representing various types of interchanges with different geometric and traffic characteristics. Video cameras, mounted on existing poles on the side of the road and on nearby buildings, were used to gather traffic operation data, including demand, lane utilization, and queue length at each site. The research evaluated both individual analytic model components (such as lane utilization factors and internal queue length) and the performance of the interchange (reflected in average queue lengths and control delay). Overall, the models performed well. However, large discrepancies were observed when operating conditions of the interchange were close to capacity. The queue length prediction at the beginning of the upstream arterial or ramp phase was calibrated to modify the effective green time estimation. A new lane utilization model was based on field data for a four- or five-lane external arterial approach where the two leftmost lanes were extensions of the downstream dual left turn lanes. The findings of the work were incorporated into the 2010 Highway Capacity Manual.

Application of Inverted Function to Alignment Optimization Design of Interchange Ramp

For adopting to the difficult terrain and restricted conditions, a probability of using the concept of inverted function into interchange linear to optimized design is built, which use the inverted function y=a/x as the interchange right-turn ramp linear. This function can be corresponded to the vehicle trajectory, decrease the area and cut the cost of interchange compared with the ordinary way“spiral-circle-spiral”.By the analysis of how to use this function linear to be ramp, this paper get the way to set the ends of the ramp by circular curve or spiral curve. And this paper also take application example to illustrate the specific solution of how to use the inverted function to set the interchange right-turn ramp.

Provision of Sight Distance around Concrete Barriers and Structures on Freeways and Interchanges

The use of concrete barriers 1.1 m (3.6 ft) high at both median and outer-shoulder edges of freeways is common in Australia. The use of such barriers is also common on interchange ramps on or under structures. Where curved ramps form an overpass of a major road or a road crosses a rail line, concrete barriers 1.4 m (4.6 ft) high and larger are used. The provision of criteria for normal stopping sight distance around these concrete barriers and other structures such as bridge abutments and retaining walls on horizontal curves (and on combinations of horizontal and vertical curves) can lead to a requirement for extremely wide shoulders. Such shoulder widths were often considered uneconomical, and only narrow shoulders were provided. This choice was either based on some artificially low design speed or, even worse, was made by ignoring the sight distance requirements altogether and simply providing what was considered to be practical. This paper discusses new criteria for the provision of sight distance around barriers and structures, as documented in the 2009 release of the Austroads Guide to Road Design series. The new criteria achieve practical, yet justifiable, results.

Guidelines for Spacing between Freeway Ramps

Existing geometric design guidance related to interchange ramp spacing in the Texas Roadway Design Manual and AASHTO's Policy on Geometric Design of Highways and Streets is not speed dependent even though intuition indicates that spacing and speed are related. Understanding the relationship between interchange ramp spacing, speed, and freeway operations is important, especially in developing potential design values for higher speeds (e.g., 85 to 100 mph). The objectives of this Texas Department of Transportation project were (a) to investigate relationships between weaving length, speed, and overall vehicle operations for successive ramps on Texas freeways and (b) to propose updates to current guidance on recommended distances between ramps. Several methods were used to assist in developing guidance on ramp spacing lengths. The methods and resources used to generate potential lengths included (a) guidance provided in the Design Manual for Roads and Bridges published by the Highways Agency in England, (b) minimum deceleration and acceleration lengths for freeway conditions, (c) decision sight distance, (d) sign spacing needs, (e) NCHRP Project 3–75 findings, (f) findings from field studies at seven sites in Texas, (g) findings from simulation conducted as part of this research, and (h) safety relationships identified in the literature. Suggested ramp spacings were developed for the entrance–exit and exit–exit ramp scenarios.

Evaluation of Pavement Friction Performance on Interchange Ramps at Network Level

Most state highway agencies conduct inventory friction testing on mainline highways to monitor network pavement friction performance. However, no state highway agencies have been reported to monitor pavement friction performance on interchange ramps. Interchange ramps constitute a large portion of the interstate highway facilities. Great concerns have arisen nationwide due to the increasing number of accidents in the ramp areas. This paper presents an effort to evaluate pavement friction performance on interchange ramps in Indiana. It is found that the overall average posted speed is 38 mi/h on interchange ramps, which is close to the test speed of 64 km/h recommended by AASHTO for establishing pavement friction requirements. In addition, pavement friction seemed to decrease as ramp curvature decreased. In general, three tests at the entrance, midpoint, and exit can provide information sufficient to evaluate pavement friction performance on an entire ramp. The 15th percentile friction number for overall interstate mainline pavements is 30 and 29 for the selected ramps.

Crash Prediction Models for Rural Motorways

In this paper, crash prediction models for estimating the safety of rural motorways are presented. Separate models were developed for total crashes and severe (fatal plus all injury) crashes. Generalized linear modeling techniques were used to fit the models, and a negative binomial distribution error structure was assumed. The study used a sample of 2,245 crashes (728 severe crashes) that occurred from 2001 to 2005 on Motorway A16 between Naples and Canosa in Italy. Many characteristics of the motorway were substandard. The motorway allowed investigation of a wide spectrum of geometric configurations. The models were developed by the stepwise-forward procedure with explanatory variables related to traffic volume and composition, horizontal alignment, vertical alignment, design consistency, sight distance, roadside context, cross section, speed limits, and interchange ramps. The decision to keep a variable in the model was based on two criteria. The first was whether the t-ratio of the variable's estimated coefficient was significant at the 5% level. The second criterion was related to the improvement of goodness-of-fit measures of the model that includes that variable. Goodness-of-fit measures were the parameter Rα2 and Akaike's information criterion. All the parameters have a logical and expected sign. The most important result was that design consistency measures significantly affected road safety, not only on two-lane rural highways, but also on motorways.

Aesthetics, Design-Build, and Workhorse Bridges

Design requirements for workhorse bridges, such as highway overpasses, underpasses, and interchange ramps, traditionally have been oriented to addressing site constraints, conforming to codes and standards, meeting utilitarian needs, and minimizing construction costs. This practice of exclusively addressing economic and utilitarian requirements has often resulted in a highway landscape that the public characterizes as monotonous or disconnected from the surrounding urban or natural environment. This concern regarding the aesthetics of workhorse bridges has been voiced during the public involvement process. However, many projects are financially constrained, and there is often no dedicated budget for aesthetic enhancements. One of the challenges facing the workhorse bridge designer is how to define cost-effective design strategies to respond to public concerns regarding aesthetics. One approach to addressing aesthetic concerns on workhorse bridges has been developed by design-build teams. Transportation agency owners increasingly have used the design-build process for construction of highway construction projects. Increasingly, the scope of contemporary design-build projects includes requirements related to their visual character. Some of the approaches and strategies to aesthetics that design-build teams have developed are examined, and suggestions are made for ways that these can be applied to more conventional procurement methods. In addition, a case study of a project on I-25 in Colorado Springs, Colorado, is presented to illustrate the relationship of a designer-builder's approach to aesthetics.

Predicting the frequency of median barrier crashes on Pennsylvania interstate highways

Median barrier warrant criteria were developed in the 1970s and generally remain unchanged today. Vehicle travel, including both traffic volumes and operating speeds, have increased over this same time period. Encroachments into the median, and subsequent collisions with vehicles traveling in the opposite travel lanes, result in high severity crashes. Median barrier is typically used to prevent cross-median crashes; median barrier selection is based on median width and traffic volumes. Quantifiable information regarding the effects of median barrier installation and its placement on crash frequency is limited. This paper investigates median barrier crash frequency on Pennsylvania Interstate highways, including separate models for the Turnpike and all other Interstate-designated highways. Negative binomial regression models were used to develop predictive crash frequency tools. Traffic volume, horizontal alignment, interchange ramp presence, and median barrier offset distance from the travel lanes were used to estimate median barrier crash frequency. The analytical methodology developed in this research can be used, in concert with other prediction models, to assess the consequences of median barrier placement decisions.

Some Guidelines for Selecting Microsimulation Models for Interchange Traffic Operational Analysis

There are several commercially available traffic simulation packages that are able to model the full range of interchange ramp terminals. Each of these packages has pros and cons for simulating various types of interchanges and traffic control plans. Previous research has studied specific simulators in terms of their capabilities for simulating single urban point interchanges (SPUIs) and diamond interchanges. There is no guidance provided however on how to generally select appropriate simulators based on their capabilities and internal algorithms for analyzing specific interchange design and control scenarios. This paper focuses on identifying the elements that should be available in a simulator in order to evaluate a specific interchange scenario (including type, geometry, and traffic control characteristics). The paper does not identify all the specific packages that are appropriate for a specific scenario because these evolve constantly; even though the current version of a package may not support a particular function, future versions of that package may incorporate it. Thus, identifying the most appropriate package would very quickly become obsolete. It is up to the analyst to examine whether a particular characteristic or algorithm is present in a specific package. To accomplish this, three simulators were selected and studied: AIMSUN, CORSIM, and VISSIM. Data from two interchanges (one SPUI and one diamond interchange) at Arizona were obtained and used in the assessment of these packages. The model parameters and assumptions are examined for each model. Simulation is conducted first by using default parameter values followed by a calibration process to adjust parameters related to driver behavior, vehicle performance, and others. In conclusion, several elements are identified as critical in simulating interchanges, which fall in the following categories: (1) the capability of representation of specific geometric characteristics; (2) the capability of simulating specific signal control plans; (3) calibration needs and accuracy in comparison to field conditions; (4) the extraction of specific performance measures from the simulator; and (5) other observations from the research.

Part 2: Traffic Signal Systems: Integration of Diamond Interchange and Ramp Metering Operations

The aim of this research was to develop operational strategies for integrating the operations between diamond interchange traffic signals and ramp metering signals. Integrated operational strategies were developed on the basis of the two commonly used diamond interchange phasing schemes: the basic three-phase scheme and the Texas Transportation Institute four-phase scheme. The key elements of the integration system and its operations include a proposed enhanced detection system and an operational algorithm. Through implementation of special signal timings at the diamond interchange, the traffic flows feeding the ramp meters can be effectively controlled and thus minimize ramp queues and the resulting need to flush the queues, which would possibly lead to freeway breakdown. The operational strategies were evaluated with VISSIM microscopic simulation under three general traffic demand scenarios—low, medium, and high—as characterized by the volume-to-capacity ratios at the metered ramps. The results of the e...

Integration of Diamond Interchange and Ramp Metering Operations

The aim of this research was to develop operational strategies for integrating the operations between diamond interchange traffic signals and ramp metering signals. Integrated operational strategies were developed on the basis of the two commonly used diamond interchange phasing schemes: the basic three-phase scheme and the Texas Transportation Institute four-phase scheme. The key elements of the integration system and its operations include a proposed enhanced detection system and an operational algorithm. Through implementation of special signal timings at the diamond interchange, the traffic flows feeding the ramp meters can be effectively controlled and thus minimize ramp queues and the resulting need to flush the queues, which would possibly lead to freeway breakdown. The operational strategies were evaluated with VISSIM microscopic simulation under three general traffic demand scenarios–-low, medium, and high–-as characterized by the volume-to-capacity ratios at the metered ramps. The results of the evaluation indicated that the integrated operations were most effective under a medium traffic demand scenario in preventing or delaying the onset of ramp metering queue flush, thereby reducing freeway breakdown and system delays.

Methodology for Evaluating the Operational Performance of Interchange Ramp Terminals

Interchange ramp terminals are critical components of the highway network. They provide the connection between various highway facilities (e.g., freeway–arterial and arterial–arterial), and their safe and efficient operation is essential. The objective of this research was to develop improved methods for capacity and quality-of-service analysis of interchange ramp terminals. The research focuses on at-grade intersections but not on the freeway proper. All geometric configurations and interchange types except trumpet interchanges are considered, and the scope of the research includes only signalized interchanges and not “Stop” sign–controlled interchanges and roundabouts. The development of the analytical methodology is primarily based on simulation. The reason for using simulation is that adequate samples of field data are not available, and it is prohibitively expensive to collect them for all types of interchange configurations. The research team assessed several simulation models that were identified as capable of simulating all types of interchange ramp terminals and selected the most appropriate one for model development. Once a simulation model was selected, a variety of interchange configurations were simulated, and selected measures of effectiveness were obtained. Analytical models were developed on the basis of the results of simulation to predict different measures, such as average control delay, volume-to-capacity ratio, and queue-to-storage ratio, for a variety of design and traffic control characteristics.

Methodology for Evaluating the Operational Performance of Interchange Ramp Terminals

Interchange ramp terminals are critical components of the highway network. They provide the connection between various highway facilities (e.g., freeway-arterial and arterial-arterial), and their safe and efficient operation is essential. The objective of this research was to develop improved methods for capacity and quality-of-service analysis of interchange ramp terminals. The research focuses on at-grade intersections but not on the freeway proper. All geometric configurations and interchange types except trumpet interchanges are considered, and the scope of the research includes only signalized interchanges and not Stop sign-controlled interchanges and roundabouts. The development of the analytical methodology is primarily based on simulation. The reason for using simulation is that adequate samples of field data are not available, and it is prohibitively expensive to collect them for all types of interchange configurations. The research team assessed several simulation models that were identified a...

Radius Requirements for Reverse Horizontal Curves on Three-Dimensional Alignments

Horizontal reverse curves are used in all types of highways either in mainline alignments or in freeway interchange ramps. At present, minimum radius requirements for reverse curves are determined based on vehicle performance on each arc of the reverse curve individually without giving any consideration to the nature of the reverse curvature. This paper determines the required minimum radius for reverse curves on freeway mainlines based on vehicle stability using computer software to simulate truck behavior on different alignments. It was found that an increase to the minimum radius requirements of horizontal reverse curves is required to maintain the driver comfort levels suggested by design guides and to prevent potential rollover. That increase ranges from 8.3 to 28.8% depending on the geometric configuration of the highway as well as on the design vehicle. The design guidelines developed for horizontal reverse curves should be useful in improving road safety on highways, especially for freeway interchanges.