Freeway Entrance Ramps Research Articles

A Simulation‐Based Optimization Method for Truck‐Prohibit Ramp Placement along Freeways

The increasing number of trucks has a negative impact pertinent to efficiency and safety concerns on the operation of mixed traffic flow along freeways, especially at freeway entrance and exit ramps. To address such issue, this study proposes a simulation‐based method for truck‐prohibit ramp placement along freeways. The method framework contains two parts: the first part is to generate a set of new truck restriction schemes using simulation experiments, and the second part is to evaluate the generated schemes and find out the current optimal location of truck‐prohibit ramps based upon the AHP‐TOPSIS method. Three patterns of evaluation indicators are utilized to estimate the performance of freeway service in terms of traffic efficiency, road safety, and accessibility. A case study of the Beijing‐Hong Kong‐Macao freeway within Henan Province, China, is conducted to verify the effectiveness of the proposed method. Results could provide beneficial insights on the optimal location setting of truck‐prohibit ramps to enhance the entire performance of mixed traffic flow along freeways.

Driver Behavior on Freeway Entrance Ramp Terminals

AbstractThis paper studied driver behavior on freeway entrance ramp terminals using trip data from the SHRP-2 Naturalistic Driving Study (NDS) database from two different US states. The study inclu...

2258 - Impact of Different Ramp Metering Strategies on Vehicle Emissions along Freeway Segments

2nd Highest Scoring Abstract: Undergraduate/Masters Background Air pollutants are widely recognized as the substances that adversely affect the global climate, plants and animal species and public health. Certain strategies have been proposed to reduce vehicle emissions, such as the ecology oriented pavement designs and green road operations. A ramp meter is typically installed on a freeway entrance ramp to regulate the traffic flow entering a freeway according to actual traffic conditions. Ramp meters could reduce traffic congestion through adjusting ramp traffic flows to minimize the disruptions on mainline traffic flows. While there is plenty of mobility and safety related research on ramp metering, there are relatively fewer studies on the estimation of specific impacts of ramp metering on freeway emissions. Methods The objective of this research is to estimate emissions while driving along mainline freeways with a series of ramps that are controlled by meters. The vehicle emissions were estimated based on the instant vehicle speed and acceleration rate through dynamic vehicle operating modes defined by EPA MOVES. Real time driving speed and acceleration rate were measured from a test vehicle driving along the freeway I-45 in Houston, TX, where five on-ramps were placed with three control mode: (1) no metering, (2) isolated metering, and (3) integrated metering. Results During rush hours of a weekday, the isolated and integrated ramp metering strategies could improve the mobility, therefore reducing travel delay; and prevent harder acceleration and deceleration from being operated. The integrated metering strategy is more beneficial to the mobility improvement and smooth vehicle maneuver than the isolated one, which is reflected by the dominant distribution of the operational mode IDs as well. However, the ramp metering control strategy is not always favorable to vehicle emissions. The total mainline freeway emissions estimated under the isolated ramp metering strategy are higher than the no metering strategy. Conclusions Isolated and integrated ramp metering control strategies could improve mobility and enhance smooth vehicle maneuver in the mainline of a freeway. In the mean time, only when the mobility is significantly improved, such as the one in the integrated ramp metering control strategy, the total emissions are tremendously reduced for the shorter emission duration. Therefore, the integrated ramp metering control strategy is superior to the isolated control strategy, in terms of both mobility and vehicle emissions.

2258 - Impact of Different Ramp Metering Strategies on Vehicle Emissions Along Freeway Segments

Air pollutants are widely recognized as the substances that adversely affect the global climate, plants and animal species and public health. Certain strategies have been proposed to reduce vehicle emissions, such as the ecology oriented pavement designs and green road operations. A ramp meter is typically installed on a freeway entrance ramp to regulate the traffic flow entering a freeway according to actual traffic conditions. Ramp meters could reduce traffic congestion through adjusting ramp traffic flows to minimize the disruptions on mainline traffic flows. While there is plenty of mobility and safety related research on ramp metering, there are relatively fewer studies on the estimation of specific impacts of ramp metering on freeway emissions. The objective of this research is to estimate emissions while driving along mainline freeways with a series of ramps that are controlled by meters. The vehicle emissions were estimated based on the instant vehicle speed and acceleration rate through dynamic vehicle operating modes defined by EPA MOVES. Real time driving speed and acceleration rate were measured from a test vehicle driving along the freeway I-45 in Houston, TX, where five on-ramps were placed with three control mode: (1) no metering, (2) isolated metering, and (3) integrated metering. During rush hours of a weekday, the isolated and integrated ramp metering strategies could improve the mobility, therefore reducing travel delay; and prevent harder acceleration and deceleration from being operated. The integrated metering strategy is more beneficial to the mobility improvement and smooth vehicle maneuver than the isolated one, which is reflected by the dominant distribution of the operational mode IDs as well. However, the ramp metering control strategy is not always favorable to vehicle emissions. The total mainline freeway emissions estimated under the isolated ramp metering strategy are higher than the no metering strategy. Isolated and integrated ramp metering control strategies could improve mobility and enhance smooth vehicle maneuver in the mainline of a freeway. In the mean time, only when the mobility is significantly improved, such as the one in the integrated ramp metering control strategy, the total emissions are tremendously reduced for the shorter emission duration. Therefore, the integrated ramp metering control strategy is superior to the isolated control strategy, in terms of both mobility and vehicle emissions.

Methods of dropping auxiliary lanes at freeway weaving segments

ABSTRACTAuxiliary lanes connecting freeway entrance and exit ramps provide additional space for entering and exiting vehicles to change lanes. The method of dropping auxiliary lanes is critical in the design of freeway auxiliary lanes. This study investigates the performance of different methods of dropping auxiliary lanes. Case studies were conducted at two selected freeway segments with successive entrance or exit ramps in the City of Houston. Traffic simulation analysis results of these two case studies show that additional operational benefits can be achieved by extending an auxiliary lane beyond the freeway weaving segment. The study also found that if the weaving segment is followed by an entrance/exit ramp and this ramp has high traffic volume, it can be less operationally favorable to extend and terminate the auxiliary lane at this entrance/exit ramp location. Instead, dropping the auxiliary lane before this entrance/exit ramp represents a more operationally effective option.

Feasibility of Using a Constant Acceleration Rate for Freeway Entrance Ramp Acceleration Lane Length Design

AbstractWhen estimating the required acceleration length of vehicles accelerating from a stopped position, a constant acceleration rate is sometimes assumed for the sake of simplicity. Nevertheless...

이산 슬라이딩모드 제어를 이용한 램프 미터링 제어

Ramp metering is one of the most efficient and widely used control methods for an intelligent transportation management system on a freeway. Its objective is to control and upgrade freeway traffic by regulating the number of vehicles entering the freeway entrance ramp, in such a way that not only the alleviation of the congestion but also the smoothing of the traffic flow around the desired density level can be achieved for the maintenance of the maximum mainline throughput. When the cycle of the signal detection is larger than that of the system process, the density tracking problem needs to be considered in the form of the discrete-time system. Therefore, a discrete-time sliding mode control method is proposed for the ramp metering problem in the presence of both input constraint in the on-ramp and exogenous disturbance in the off-ramp considering the random behavior of the driver. Simulations were performed using a validated second-order macroscopic traffic flow model in Matlab environment and the simulation results indicate that proposed control method can achieve better performance than previously well-known ALINEA strategy in the sense that mainstream flow throughput is maximized and congestion is alleviated even in the presence of input constraint and exogenous disturbance.

HMM and HSS Based Social Behavior of Intelligent Vehicles for Freeway Entrance Ramp

In this paper, a novel approach of intelligent vehicle to interact and cooperate with other human driving vehicles is proposed at the freeway entrance ramp scenario. The system consists of a Safety Alert Module and Vehicle Control Module. The Safety Alert System module includes intention estimation and conflict judgment. A two dimension Hidden Markov Model (2DHMM) is used to estimate social vehicle’s driving intention in the intention estimation module. Then the conflict judgment module predicts the potential conflicts between the intelligent vehicle and social vehicle. Moreover, the hybrid state system (HSS) is introduced to control the intelligent vehicle while considering its decision making, states and dynamics. Co-simulation using PreScan and Simulink is conducted. The experiment results show that the intelligent vehicle performs well with a commendable social behavior in the freeway entrance ramp.

Study of Dynamic Adjustment to the Freeway Entrance Ramp Based on VISSIM

This paper aimed at the freeway entrance ramp control principles, through introduction of dynamic adjustment system of the entrance ramp and the control algorithm of the difference between traffic demand and capacity, a problem of the dynamic adjustable rate’s selection was proposed, then used the micro-simulation tool VISSIM to analysis the influence of dynamic adjustable rate that under different capacity reduction factors, choosing delay time and travel time as the standard of entrance ramp control system. At last, this paper concludes that the best reduction factor is 0.98 times the capacity.

Analysis Framework for Evaluation of Traffic Compliance Measures

Agencies and practitioners often test innovative strategies for improving driver compliance with traffic regulations. However, in evaluating these strategies, researchers often rely on simple before-and-after methods that suffer from several flaws and that can result in misleading results and an inaccurate assessment of a strategy's effectiveness. This paper examines these flaws, proposes a framework that avoids or corrects for them, and then uses it to analyze the effectiveness of a common strategy: installation of larger signage (at a freeway entrance ramp). The framework described in this paper can be applied to a wide range of driver compliance situations. Among them are yielding at pedestrian crossings, speed limit obedience, and proper anticipation of roadway features such as speed humps or intersections.

A Discussion on the Current MUTCD Standards on Traffic Control Signals for Freeway Entrance Ramps

ABSTRACT In Section 4I.02 of the newly published Manual on Uniform Traffic Control Devices (MUTCD), standards were specified for the placement of signal heads for traffic control signals at freeway entrance ramps, or ramp meters. For simultaneous operations, i.e. when ramp control signals are operated such that green signal indications are always displayed simultaneously to all of the lanes on the ramp, a minimum of two signal faces per ramp shall face entering traffic. For staggered operations, i.e. the ramp control signal are operated such that green signal indications are not always displayed simultaneously to all of the lanes on the ramp, one signal face shall be provided over the approximate center of each separately-controlled lane. Based on a nation-wide survey, it was realized that the two standards did not fully reflect the state-of-the-practice with respect to ramp metering operations. Due to the lack of significant conflicting movements at ramp meters, for any on-ramp lane, a minimum of one overhead mounted, or one upper and one lower roadside-mounted signal face is sufficient to control the metering operations. The minimum necessary number of signal faces changes according to the total number of lanes, how the signal faces are mounted (overhead or roadside mounting), and how the meters are operated (simultaneous or staggered). Suggestions are made to revise the two standards to better reflect the current nation-wide practices, and better consider the specific operational needs for ramp meters.

Thinking outside the Box to Expand Metropolitan Travel Choices

The multimodal expressway system is a concept of introducing travel choices for suburban commuters in major metropolitan areas relatively quickly and inexpensively. The entire existing limited-access highway system would provide for free flow of carpool vehicles and buses by temporarily slowing (or stopping) and releasing excess traffic at freeway entrance ramps and on the freeway main line at a series of concentric cordon locations around the core of the metropolitan area. At these locations, travel lanes would be created on the shoulder and restricted to use by buses and high-occupancy vehicles with three or more persons and would allow them to bypass the slower moving metered general-purpose traffic. A multicentered bus rapid transit system would serve commute trips between suburban residential areas and major employment centers. The transit system would be supplemented with a flexible carpooling system. An enhanced version of the concept would introduce variable peak period tolls to encourage further mode shifts, reduce traffic demand, and help pay for system costs. Sketch planning estimates of costs for freeway, transit, and flexible carpooling investments suggested that the capital costs could be self-financed through road-pricing revenues.

Approximated headway distributions for non-signalized and signalized freeway entrance ramps

Cumulative interarrival time (IAT) distributions for four different non-signalized entrance ramps (three ramps with a single lane, one ramp with two lanes) and two different signalized entrance ramps (both with a single lane) were established which can be used in digital computer traffic simulation models. The cumulative IAT distributions for the signalized and non-signalized entrance ramps were compared with each other and with the cumulative IAT distributions of the lanes for freeways. The comparative results showed that the cumulative IAT distributions for non-signalized entrance ramps are very close to the leftmost lane of a 3-lane freeway where the maximum absolute difference between the cumulative IAT distribution of the leftmost lane of a 3-lane freeway and the entrance ramps cumulative IAT distribution was 3%. The cumulative IAT distribution for the signalized entrance ramps was found to be different from the non-signalized entrance ramp cumulative IAT distribution. The approximated cumulative IAT distributions for signalized and non-signalized entrance ramp traffic for any hourly traffic volume from a few vehicles/hour up to 2500 vehicles/hour can be obtained at http://www.ohio.edu/orite/research/uitds.cfm.

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.

Viewing Ground-Mounted Diagrammatic Guide Signs Before Entrance Ramps at Night: Driver Eye Scanning Behavior

The driver eye scanning study is part of a larger study conducted for the Ohio Department of Transportation to evaluate the effectiveness of ground-mounted diagrammatic guide signs placed before entrance ramps at highway freeway interchanges. This nighttime study investigated driver eye scanning behavior while approaching ground-mounted diagrammatic guide signs placed before entrance ramps. Six highway-freeway interchanges were selected in the Greater Columbus, Ohio, area for placement of the diagrammatic signs in the field. Subjects were six unfamiliar drivers, between the ages of 22 to 42. Two diagrammatic signs were located at each of the six interchanges, .5 mi (805 m) and .25 mi (402 m) before the last point of the gore, where a driver can still gain access to the correct freeway entrance ramp. Driver eye scanning behavior measurements were recorded at night to determine if the presence of the diagrammatic signs elicited an excessive number of eye fixations or was visually distracting to the drivers or both. The results indicate that the diagrammatic signs are not looked at excessively often or excessively long. The average look numbers and average look duration times indicate a normal and reasonable level of information acquisition processing employed by the drivers. These values agree with those previously obtained for regular traffic signing determined in previous eye scanning studies. Ground-mounted diagrammatic signs on multilane arterials in advance of highway freeway interchanges were not demonstrated to unduly distract drivers and detrimentally affect a driver’s looking behavior.

Effectiveness of Ground-Mounted Diagrammatic Advance Guide Signs for Freeway Entrance Ramps

This study investigated the effectiveness of ground-mounted diagrammatic signs in the context of urban multilane arterials leading to freeways. Six highway-freeway interchanges were selected in the greater Columbus, Ohio, area for installation of the diagrammatic signs in the field. The primary measure of effectiveness was the distance at which unfamiliar drivers driving in the wrong lane changed lanes. A total of 21 and 19 test drivers unfamiliar with Columbus roads were recruited for an evaluation before and after installation of the diagrammatic guide signs. This evaluation with unfamiliar test drivers showed that drivers were able to execute a needed lane change earlier when diagrammatic signs were provided. Combining all six sites and looking at the 50th (377 m before, 819 m after) and 85th percentile (203 m before, 601 m after) lane change distances, an increase by a factor of 2.2 to 3.0 between the after and before condition was observed. In addition, a panel of 13 Ohio Department of Transportation and FHWA evaluators visited the six interchange sites and provided their input and opinions on the use of diagrammatic signs. The majority of the evaluators fully embraced the idea of diagrammatic signs. It is suggested that such signs should be used on multilane arterials in advance of highway–freeway interchanges in addition to preexisting guide signs (trailblazer assemblies), in cases in which the cost of overhead span-type sign bridges cannot be economically justified and additional advance guidance information to motorists is highly desirable.

Utilization of Double Left-Turn Lanes with Downstream Lane Reductions

The capacity of left-turn movements at signalized intersections is sometimes increased by using two exclusive double left-turn lanes at the intersection followed by a reduction to a single lane after the turn is made. A typical application is the use of double left-turn lanes onto a freeway entrance ramp, where the right lane is dropped in advance of the merge area. The effectiveness of the “added” outside left-turn lane and downstream auxiliary lane depends on the amount of traffic using that lane. While equal distribution of traffic between a continuous and an auxiliary through lane would result in the greatest total capacity of this lane pair, traffic and geometric factors are usually such that this does not occur. The 1994 Highway Capacity Manual does not address intersection configurations with downstream lane reductions. This paper describes the development of a mathematical model, based on field data, which does predict auxiliary lane use for this intersection configuration.

Modeling vehicle acceleration deceleration behavior during merge maneuvers

Freeway merge maneuvers are complex and may involve a lane change, continuous acceleration, possible deceleration, and finally a gap acceptance. This paper presents a methodology to model ramp vehicle acceleration-deceleration behavior at freeway entrance ramps. Primary data capturing a wide range of information were collected using video tape methods and manually reduced through image processing techniques. Ramp vehicle merging position in conjunction with freeway and ramp flow levels was analyzed for both parallel and taper type entrance ramps. Where vehicle trajectory data were available, merging positions with respect to ramp vehicle speed as well as relative speed and time gap between a ramp vehicle and freeway vehicles were examined. Results show that the merge position has a statistically insignificant effect upon individual traffic parameters. Methodology presented in this paper used the stimulus-response equation as a fundamental rule to model ramp vehicle acceleration=deceleration behavior. The timebase car-following model was modified to a nonlinear distance-base stimulus-response equation to capture the characteristics of the collected traffic data. Calibration of the proposed nonlinear model from a pilot study demonstrated satisfactory results and indicated that a time lag before ramp drivers respond to stimuli does exist. Effects of surrounding freeway vehicles on ramp vehicle acceleration-deceleration behavior were found to be significant. (A)

Visibility of New Dashed Yellow and White Center Stripes as Function of Material Retroreflectivity

Economic and environmental concerns have raised questions about the continued use of yellow center lines on two-lane highways and yellow left-edge lines on divided highways or freeway entrance and exit ramps. The use of yellow pavement markings as a warning to indicate opposing traffic appears to be a concept that is compatible with certain human factors population stereotypes and accepted industry standards (yellow for caution), but it is unclear how well the general driver population understands the message conveyed by yellow pavement markings. Another question is how the visibility of yellow center lines or left-edge lines compares with the visibility of similar white pavement markings. The effects of color (white and yellow) and material retroreflectivity (low, medium, and high) on the end detection distance of finite-length center lines at night under automobile low-beam illumination were determined. Ten subjects were used in a field experiment (rural, automobile low-beam conditions) to obtain the end detection distances of finite-length center stripes of 0.1-m width. The data show that the end detection distances of new yellow dashed center stripes and new white dashed center stripes are about the same. The average end detection distance was 30 to 35 m for the low-retroreflectivity material and about 62 m for the high-retroreflectivity material (four- to fivefold retroreflectivity increase). It is tentatively concluded that the use of white center stripes most likely will not result in a significant increase in the end detection distance when compared with the use of similar yellow center stripes. It is also tentatively concluded that an increase in the retroreflectivity of the pavement marking materials will result in a significant and desirable increase of the visibility distance, but to provide a minimum preview time of 3.6 sec (at a vehicle speed of 90 km/hr), even higher-retroreflectivity materials than the ones used in this study will be required.

Visibility of New Dashed Yellow and White Center Stripes as Function of Material Retroreflectivity

Economic and environmental concerns have raised questions about the continued use of yellow center lines on two-lane highways and yellow left-edge lines on divided highways or freeway entrance and exit ramps. The use of yellow pavement markings as a warning to indicate opposing traffic appears to be a concept that is compatible with certain human factors population stereotypes and accepted industry standards (yellow for caution), but it is unclear how well the general driver population understands the message conveyed by yellow pavement markings. Another question is how the visibility of yellow center lines or left-edge lines compares with the visibility of similar white pavement markings. The effects of color (white and yellow) and material retroreflectivity (low, medium, and high) on the end detection distance of finite-length center lines at night under automobile low-beam illumination were determined. Ten subjects were used in a field experiment (rural, automobile low-beam conditions) to obtain the end detection distances of finite-length center stripes of 0.1-m width. The data show that the end detection distances of new yellow dashed center stripes and new white dashed center stripes are about the same. The average end detection distance was 30 to 35 m for the low-retroreflectivity material and about 62 m for the high-retroreflectivity material (four- to fivefold retroreflectivity increase). It is tentatively concluded that the use of white center stripes most likely will not result in a significant increase in the end detection distance when compared with the use of similar yellow center stripes. It is also tentatively concluded that an increase in the retroreflectivity of the pavement marking materials will result in a significant and desirable increase of the visibility distance, but to provide a minimum preview time of 3.6 sec (at a vehicle speed of 90 km/hr), even higher-retroreflectivity materials than the ones used in this study will be required.