Entrance Ramp Research Articles

Failures of Feedback: Rush Hour Along the Highway to Obesity

From hot dogs to Hashimoto's and inheritance to inactivity, many "entrance ramps" converge onto the "Highway to Obesity", each contributing caloric intake that exceeds expenditure. Initially, the hypothalamus regulates appetite and energy based on leptin feedback, until feedback failure increases appetite, and allows deposition of abdominal fat, metabolic dysregulation, and metabolic syndrome. Without feedback controls, progress toward obesity is unimpeded unless diet, exercise, and/or medications provide an exit ramp.

Obesity and Metabolic Syndrome Overview

1. Wayne Gade, PhD, MT(ASCP)[⇑][1] 1. Associate Professor, Clinical Lab Science Program, University of Illinois Springfield, Springfield, IL 2. Jean Gade, MS, BS(RN) 1. Nurse Educator, Lincoln Prairie Behavioral Health, Springfield, IL 1. Address for Correspondence: Wayne Gade, Clinical Laboratory Science & Chemistry Departments, HSB Rm 314, One University Place, Springfield, IL 62703, wgade1{at}uis.edu, 217-725-6384. Modern societies suffer from an obesity epidemic, despite considerable societal pressure to be thin. The epidemic persists in spite of the widely accepted notion that obesity is unhealthy, unattractive, and shortens life expectancy. Conservation of energy (the first law of thermodynamics) tells us that obesity must result when caloric intake chronically exceeds caloric expenditures. Historically, physiologic control mechanisms suppressed appetite and promoted physical activity, enabling most people to avoid a positive energy balance. But what forces compel modern humans, the most intelligent and rational of beings, to chronically exceed their caloric requirements? In the first article, we compare the development of obesity to a “highway” whose destination is obesity. This “Highway to Obesity” has many “entrance ramps” that represent the many biological, genetic, and psychological factors that underlie overindulgence. We explore the genetic deficiencies and biological tendencies that predispose one toward obesity. In recent decades, these inherited tendencies toward obesity are more likely to be expressed, due to easy access to high calorie foods and decreased physical activity. Complete genetic deficiencies rarely occur and generally result in early-onset, morbid obesity. More commonly, obesity involves a gradually acquired dysregulation of hormonal systems that initially limit obesity. However, when these fragile feedback mechanisms become overwhelmed and fail, hormone resistance actually favors weight gain. Article one also examines the multitude of comorbidities associated with obesity. These include type II diabetes, atherosclerosis, hypertension, congestive heart failure, pulmonary disease, several forms of cancer; renal disease, liver and gall bladder diseases, polycystic ovarian syndrome, coagulation disorders,… [1]: #corresp-1

Truck Acceleration Speeds and Distances at Weigh Stations

Tractor-trailer trucks accelerating on freeway entry ramps and entering the main traffic lanes require greater lengths to accelerate than do passenger vehicles. As freeway volumes have grown over the decades, entry ramp junction designs that were once adequate now experience congestion at weigh stations and other locations where higher volumes of trucks enter the freeway. The acceleration lengths and speeds of tractor-trailers accelerating onto freeways were measured at five vehicle weigh stations. Other data obtained and analyzed included truck weights, freeway volumes, and freeway grades. Models were developed to predict tractor-trailer speed over given acceleration lengths. From the analysis, it was concluded that longer acceleration lanes were needed for heavy vehicles leaving weigh stations to accelerate to speeds closer to the speeds on the main lanes and to be less disruptive to freeway traffic flow as the heavy vehicles merge into the main lanes. The findings also have implications for establishing the location of weigh stations, the spacing of freeway interchanges, and the setting of freeway speed limits.

Goodbye, Arkansas

51 BARRETT HATHCOCK GOODBYE, ARKANSAS I crossed the bridge the first time to amuse a girl. Her name was Clay Ann and she came from Amarillo, Texas. At the time, during that desperate fall of my freshman year, I was on her heels in the way I was on the heels of every woman who smiled twice at me. I’d call Clay Ann a neo-hippie if that wouldn’t diminish her exoticism for me. She was a hippie’s hippie , an aggressive female slacker, an endangered species at my college. She showed those hippie pretenders—with their Phish bumper stickers and compulsive Widespread Panic concert attendance and overpriced marijuana paraphernalia—how a true degenerate behaved. She came to class more than once knocked clear out of her skull on some pills but never had the druggie’s wisdom just to pipe down and not go for the daily participation grade. She would smoke pot in her dorm room with no rolledup towel underneath the door, no pretense of hiding what she was up to. She was generous and communal not only with her drugs but with her drug-related wisdom: “Barrett,” she said to me one time, “whatever happens, don’t ever do acid. You’re entirely too paranoid and insecure already. It would destroy you.” (I consider this some of the best advice I’ve ever received.) In retrospect I’d like to think she was a lesbian, but in truth she was really just not that into me. But before making this discovery I found myself driving her around Midtown Memphis one night, trying not to be boring. “Have you ever?” she asked. “No, I don’t think so.” “You need to. It’s amazing.” I gunned the engine up the incline of the entrance ramp, sending us away from the civilized light of downtown and into the dark wilderness beyond. I was nervous double-fold because this seemed like the beginning of some sort of intimacy and because I was running out of gas. Somehow I hadn’t noticed this until we’d hit the ramp onto the bridge, but there it was—the fuel gauge warning light. It bespoke of a routine personal flaw: ev- colorado review 52 ery time I pretended to be cool, to live without mundane cares, to engage in unprepared bridge-crossings, or their equivalent, the reality of the world tripped me up. Here the culprit was the willfully devious gas gauge. No matter what car, it always runs the same way: You fill it up, and it takes forever for the first quarter of a tank to disappear. The next half a tank vanishes somewhere—I’ve only been to school and the dry cleaners!— and then you’re down to the precarious last quarter of a tank. And this last purportedly equal fourth vanishes while you’re getting out of the driveway. So there we were: the fuel light alert, the needle collapsed at the end of its register, and a short life’s worth of panicky thinking about fuel and cars and the perils of wooing while driving, combining in my mind as we elevated to the bridge’s full height and its central illuminated M-shaped arch began to encage us. “Just how long is this thing?” I asked. “Look at the fucking water!” Clay Ann shrieked, her head out the window. I had fleeting concerns about the possibility of her head getting cut off by one of the passing struts, but shoved that concern aside to calculate the amount of increased drag and decimated fuel created by her open window and outside head. But then all of that was superseded by the need to keep the car in its lane and not swerve into the oncoming semitrailers. What I couldn’t notice then but would come to appreciate later was how beautiful crossing the river could be—the perpendicular highway of water glinting in the bridge light and moonlight, the car rocking along, encased in that industrial-age skeleton, one’s view broken briefly every second by a passing rib. Then I drove fast, noticing so little, while Clay Ann leaned aggressively outside, letting her...

How Lane Arrangements on Freeway Mainlines and Ramps Affect Safety of Freeways with Closely Spaced Entrance and Exit Ramps

The number and arrangement of lanes on freeways are important considerations in freeway geometric design. The objective of this study is to evaluate the safety impacts of lane arrangements on freeway segments with closely spaced entrance and exit ramps. Three different types of lane arrangements were considered. They were designated as Type A, Type B, and Type C arrangements. The research team compared crash frequency, crash rate, crash severity, and collision types for freeway segments with different types of lane arrangements. Crash prediction models were developed to relate crash counts to various explanatory variables such as traffic conditions and geometric characteristics. The crash data analysis results show that the Type C arrangement reported the lowest average crash frequency and crash rate. The Type C arrangement uses a continuous auxiliary lane to connect the entrance and exit ramps; and the auxiliary is dropped in a one-lane exit. Freeway segments with the Type B arrangement reported the highest average crash frequency, crash rate, and percentage of fatal plus severe injury crashes. Based on the crash prediction models, if other factors remain constant, a Type B arrangement results in 113% more total crashes and 102% more severe crashes than does a Type C arrangement. Crash data analysis results suggest that the Type B arrangement should be used cautiously when entrance and exit ramps are closely spaced.

Besides Google: Guiding Gifted Elementary Students onto the Entrance Ramp of the Information Superhighway

Besides Google: Guiding Gifted Elementary Students onto the Entrance Ramp of the Information Superhighway

Modeling Driver Behavior and Safety on Freeway Merging Areas

Access to freeways is provided through interchanges to maintain the design concept of uninterrupted traffic flow. Therefore, provision of an appropriate entrance ramp and acceleration lane geometry that allows the entering vehicle to accelerate to a speed closer to the through lane speed is important for comfortable and safe merging maneuvers. In this paper, speed and traffic data were collected from 23 merging sites on Highway 417 located within the City of Ottawa, Canada, to study the traffic behavior at freeway merge areas. Analysis of traffic behavior showed that merging speed depends on both ramp and speed-change lane (SCL) geometrics. Lower merging speed was shown to be associated with higher collisions on the acceleration lanes. Right lane traffic volume and merging speed of entering vehicles were shown to significantly affect right lane speed along the acceleration lane. In addition, several statistically significant models were developed for the prediction of 85th percentile passenger car right lane speed, merging speed, merging distance, and acceleration on the SCL. A safety performance model was also developed to relate the total number of collisions on the acceleration SCL to the features of the merge area including the merging speed.

Traffic Diversion Effect of Ramp Metering at Individual and System Levels

Understanding traffic diversion due to control actions is essential to the success of advanced traffic management systems such as ramp metering, arterial signal control, and traveler information services. This paper explores the systemwide traffic diversion effect of a well-documented control algorithm on a large real-world network. By using an unconventional positive approach that models how travelers actually learn the road network experientially and make heuristic route search and choice decisions in the presence of information and decision costs, this research is able to explore traffic diversion as an emergent process, with travelers’ decision-making processes individually traced. The supply-side effect of ramp metering is modeled as capacity changes at freeway bottlenecks and metered entrance ramps. Results show that only 1% of all peak-hour travelers (6,200) on the Twin Cities (Minneapolis–St. Paul), Minnesota, network change routes after meters are deployed, even though a much larger number of them (14%) are significantly hurt by the algorithm. It is also evident that ramp meters can benefit and hurt all types of roads in a large network, including freeways, local streets, and ramps. An important conclusion with practical significance is that different behavioral assumptions could produce opposing policy recommendations in traffic operations. For instance, models with normative assumptions (e.g., DUE) lead to systematic benefit overestimation because of a particular microbehavioral mechanism.

Characteristics of Breakdown Phenomenon in Merging Sections of Urban Expressways in Japan

This paper aims to investigate the breakdown phenomenon at on-ramp merging sections of urban expressways in Japan. The breakdown events are treated here as a probabilistic phenomenon. Six merging sections at which breakdowns frequently occur are selected to be different in their geometry in relation to acceleration lane length and ramp entrance side. Three different aspects of merging capacity are recognized: the maximum outflow rate before the breakdown, the outflow rate when the breakdown starts to occur, and the outflow rates during the queue discharge period. These outflow aspects are analyzed after they are converted into an equivalent passenger car unit to eliminate the effect of heavy vehicles. Then the probability of breakdown at these sections is investigated as a function of outflow rates. The observed breakdown probabilities follow the Weibull distribution function at all sections, with close values of shape parameter and wide range values of scale parameter. The values of the scale parameter are used to investigate the effects of the acceleration lane length and entrance ramp side. Moreover, the breakdown probability is investigated as a function of the occupancy observed immediately downstream of the merging section. Last, the effects of ramp flow ratio and interval length of aggregated data are discussed.

Motorway traffic parameter estimation from mobile phone counts

In this paper a new method for real time estimation of vehicular flows and densities on motorways is proposed. This method is based on fusing traffic counts with mobile phone counts. The procedure used for the estimation of traffic flow parameters is based on the hypothesis that “instrumented” vehicles can be counted on specific motorway sections and traffic flow can be measured on entrance and exit ramps. The motorway is subdivided into cells, assuming that mobile phones entering and exiting every cell can be counted during the observation period. An estimate of “instrumented” vehicle concentration is obtained and propagated on the network in time and space. This allows one to estimate traffic flow parameters by sampling “instrumented” traffic flow parameters using a “concentration” (the ratio of the densities of instrumented vehicles to the density of overall traffic) propagation mechanism.

Optimizing on-ramp entries to exploit the capacity of a road

In this paper, we perform simulations of an extended Nagel-Schreckenberg model for one-lane and two-lane roads. We consider the presence of many entry ramps, placed in different locations, and we determine how the flux of cars of each entry ramp must be controlled in order to better exploit the capacity of the road. Our results are of relevance for the optimization of daily traffic, and set rules for the design of evacuation plans of urban conglomerations exposed to natural hazards, such as volcanoes.

Vehicle sorting for platoon formation: Impacts on highway entry and throughput

Automated highway systems (AHS) are intended to increase the throughput and safety of roadways through computer control, communication and sensing. In the “platoon” concept for AHS, vehicles travel on highways in closely spaced groups. To maximize benefits, it is desirable to form platoons that are reasonably large (five or more vehicles), and it is also desirable to ensure that platoons remain intact for considerable distances. This paper develops and evaluates strategies for organizing vehicles into platoons at highway entrances, with the objective of maximizing the distance that platoons stay intact, so that they do not need to be regrouped into new platoons on the highway itself. Fundamentally, this entails grouping vehicles according to their destination. We evaluate various strategies in which vehicles are sorted on entrance ramps, with respect to platoon sizes, throughput and platoon formation time.

Effect of On-Ramp Geometric and Operational Factors on Vehicle Activity

The microscopic vehicle activity levels for a random sample of 7,288 vehicles were measured and analyzed for cars and trucks on 26 entrance ramps in Louisville, Ky. Approximately 12.3 million distance measurements were recorded and used to calculate vehicle speeds, accelerations, and power requirements. This study was performed to examine the effects of geometrical and operational characteristics on changes in vehicle activity levels on entrance ramps. Linear regression and hierarchical-based regression tree methods were used to determine the impacts of the ramp characteristics. The regression analyses revealed that grade had the greatest impact on vehicle acceleration and power requirements in the Louisville area while ramp curvature, length of curvature, and mainline traffic flow rates had impacts under specific conditions. The results of the multivariable regression produced models that could explain up to 70% of the power demand based on ramp geometric and operational characteristics.

Calibration of Predictive Models for Estimating Safety of Ramp Design Configurations

The goal for the calibration process is to use predictive models developed with data collected from other jurisdictions and apply them to the jurisdiction of interest by adapting the models for local conditions and characteristics. Given the large costs associated with data collection, this process is often the only method available to transportation agencies for estimating the safety of different transportation facilities. Thus, recalibrating models produced from other jurisdictions allows agencies to produce their own models at relatively low costs. The objective for the research was to recalibrate a set of crash prediction models for different ramp design configurations. The ramp design configurations addressed included diagonal ramps, non-free-flow loop ramps, free-flow loop ramps, and outer connection ramps. A total of 44 ramps located in and around Austin, Texas, were used in the calibration process. The results of the study showed that more crashes occur on exit ramps than entrance ramps by a ratio of about 6 to 4. The results also showed that the non-free-flow ramp experiences twice as many crashes as other types of ramp. Similarly, more crashes occur on rural than urban ramps.

Calibration of Predictive Models for Estimating Safety of Ramp Design Configurations

The goal for the calibration process is to use predictive models developed with data collected from other jurisdictions and apply them to the jurisdiction of interest by adapting the models for local conditions and characteristics. Given the large costs associated with data collection, this process is often the only method available to transportation agencies for estimating the safety of different transportation facilities. Thus, recalibrating models produced from other jurisdictions allows agencies to produce their own models at relatively low costs. The objective for the research was to recalibrate a set of crash prediction models for different ramp design configurations. The ramp design configurations addressed included diagonal ramps, non-free-flow loop ramps, free-flow loop ramps, and outer connection ramps. A total of 44 ramps located in and around Austin, Texas, were used in the calibration process. The results of the study showed that more crashes occur on exit ramps than entrance ramps by a ratio of about 6 to 4. The results also showed that the non-free-flow ramp experiences twice as many crashes as other types of ramp. Similarly, more crashes occur on rural than urban ramps.

Evaluation of Emergency Evacuation Strategies for Downtown Event Traffic Using a Dynamic Network Model

This research studied the feasibility of applying a dynamic traffic assignment model, Dynasmart-P, to evaluate the effectiveness of alternative strategies for evacuating the traffic in downtown Minneapolis, Minnesota, under a hypothetical emergency situation that included the evacuation of a sellout crowd in the Metrodome. For this study, the southwest portion of the Twin Cities metro area was selected as the study network, and a set of different network configurations was evaluated for effectiveness in coping with a given emergency situation. The simulation results indicate that managing traffic conditions at the outbound freeway links in the given network during the evacuation period and the access capacity from the downtown area to those outbound freeway links are the critical factors affecting the effectiveness of evacuation operations. For example, the evacuation time under the contraflow operations with the freeways surrounding the downtown area was substantially reduced when the capacities of the key entrance ramps were also increased.

Evaluation of Emergency Evacuation Strategies for Downtown Event Traffic Using a Dynamic Network Model

This research studied the feasibility of applying a dynamic traffic assignment model, Dynasmart-P, to evaluate the effectiveness of alternative strategies for evacuating the traffic in downtown Minneapolis, Minnesota, under a hypothetical emergency situation that included the evacuation of a sellout crowd in the Metrodome. For this study, the southwest portion of the Twin Cities metro area was selected as the study network, and a set of different network configurations was evaluated for effectiveness in coping with a given emergency situation. The simulation results indicate that managing traffic conditions at the outbound freeway links in the given network during the evacuation period and the access capacity from the downtown area to those outbound freeway links are the critical factors affecting the effectiveness of evacuation operations. For example, the evacuation time under the contraflow operations with the freeways surrounding the downtown area was substantially reduced when the capacities of the key entrance ramps were also increased.

Optimal freeway ramp control without origin–destination information

This paper develops an analytical framework for ramp metering, under which various ramp control strategies can be viewed as ramifications of the same most-efficient control logic with different threshold values, control methods, and equity considerations. The most-efficient control logic only meters the entrance ramps nearest critical freeway mainline sections so as to eliminate freeway internal queues, which is derived from a new formulation of the optimal ramp control problem. Instead of assuming the availability of real-time origin–destination information, the new formulation takes advantages of the stability and predictability of off-ramp exit percentages. Those properties of the off-ramp exit percentages are supported by empirical data, and allow us to formulate the optimal ramp control problem as a linear program whose input variables are all directly measurable by detectors in real-time. The solution is also tested on a real-world freeway section in a microscopic traffic simulator for demonstration. Time-dependent origin–destination tables and off-ramp exit percentages are compared as two alternative ways to represent the true real-time demand patterns that are important to freeway ramp metering.

Types and characteristics of ramp-related motor vehicle crashes on urban interstate roadways in Northern Virginia

Problem: Freeway entrance and exit ramp interchanges are the sites of far more crashes per mile driven than other segments of interstate highways, but the characteristics and circumstances of ramp crashes have been the subject of relatively little recent research. Method: This study examined a sample of 1,150 crashes that occurred on heavily traveled urban interstate ramps in Northern Virginia. Based on a review of diagrams and narrative descriptions from police crash reports, the most common crash types were identified and examined for different roadway locations and ramp designs and by whether at-fault drivers were entering or exiting the freeway. Results: About half of all crashes occurred when at-fault drivers were in the process of exiting interstates, 36% occurred when drivers were entering, and 16% occurred at the midpoints of access roads or on ramps connecting two interstate freeways. Three major crash types—run-off-road, rear-end, and sideswipe/cutoff—accounted for 95% of crashes in the study. The crash type most frequently associated with exiting was run-off-road, and the types most common with entering drivers were rear-end or sideswipe/cutoff. Crashes most common on ramps—run-off-road crashes—frequently occurred when vehicles were exiting interstates at night, in bad weather, or on curved portions of ramps. Speed was often a factor. Crashes occurring on ramp margins (where ramps or access roads enter or exit) were most commonly of the sideswipe/cutoff type. These often involved at-fault passenger vehicles merging from entrance ramps into the sides of large trucks already on the freeway. The predominant crash type on access roads was rear-end crashes; congestion was a factor in these crashes. Alcohol was a reported factor in a sizeable proportion of run-off-road crashes occurring on ramps (14%) and ramp margins (30%). Impact on Industry: Candidate countermeasures for run-off-road crashes include geometric design changes to increase ramp design speed such as increasing curve radii. Speed-related crashes may be reduced by the use of speed cameras accompanied by publicity. Rear-end crash countermeasures could include surveillance systems that quickly detect unexpected congestion, incident response programs, and variable message signs to alert drivers to traffic congestion ahead. Countermeasures for sideswipe/cutoff crashes could include extending the length of acceleration lanes.

Another View of Truck Lane Restrictions

As truck volumes on U.S. highways continue to increase, both elected officials and members of the general public often look to the use of lane restrictions for large trucks as a means to increase operating efficiency and highway safety. In the past, research has offered little evidence that either safety or efficiency is positively affected by widespread use of this practice. Another view of truck lane-use restrictions on high-speed, limited-access facilities is offered. To determine the effects of lane-use restrictions, scenarios that varied traffic characteristics such as volume, grade, percentage of trucks, and the presence of entrance and exit ramps were developed with the VISSIM model. In each scenario traffic along the model freeway segment was monitored to determine the effect of the lane-use restrictions by comparing values of various traffic measures from a model run first without and then again with truck lane restrictions. As in past research efforts, the implementation of truck lane restrictions in a variety of scenarios is shown to have little effect on a number of traditional measures, including average speed, speed differential between cars and large trucks, and level of service. However, further examination of data resulting from the simulation process shows that significant gains in the area of safety and driver comfort may be realized through the reduction of lane-changing maneuvers by all vehicle types, lending support to past driver surveys indicating strong support for this practice among drivers of passenger vehicles.