Deceleration Lane Research Articles

Exploring Impacts of Factors Contributing to Injury Severity at Freeway Diverge Areas

A study was done to identify factors contributing to injury severity at freeway diverge areas and to evaluate impacts of the factors. Crash data and roadway information were collected at 231 freeway exit segments in Florida. Injury severity prediction models were developed by using partial proportional odds regression, which relaxes the restriction that all regression coefficients be the same across output values and allows one or more regression coefficients to differ across outcome levels. The analysis results indicated that the partial proportional odds model is more flexible and provides much better results than does the ordered probit model for fitting injury severity data. Factors that significantly influence injury severity at freeway diverge areas include length of deceleration and ramp lanes, curve and grade at diverge areas, light and weather conditions, alcohol or drug involvement, heavy-vehicle involvement, number of lanes on main lines, average daily traffic on main lines, surface condition, land type, and crash type. It can also be concluded that exit ramp types (single-lane exit ramps, single-lane exit ramps with a taper, two-lane exit ramps with an optional lane, and two-lane exit ramps without an optional lane) have no significant effects on injury severity at freeway diverge areas.

Road Traffic Noise Prediction Model under Interrupted Traffic Flow Condition

The objective of this study is to develop an empirical traffic noise prediction model under interrupted traffic flow conditions using two analytical the approaches, the first being the acceleration lane approach and second being the deceleration approach. The urban road network of Bangalore city has been selected as the study area. Sixteen locations are chosen in major traffic junctions of the study area. The traffic noise data collected from the study locations were analyzed separately for both acceleration and deceleration lanes when vehicles leave an intersection on a green traffic light and come to a stop on red traffic light. Based on the study, a regression noise prediction model has been developed for both acceleration and deceleration lanes.

Modeling Freeway Diverging Behavior on Deceleration Lanes

Typically, deceleration speed-change lanes (SCLs) and exit ramp terminals on freeways are designed to allow vehicles to depart the freeway safely and efficiently. Freeway diverge areas with adequate SCL lengths should enable the exiting drivers to diverge off the freeway through traffic, decelerate to the desired ramp speed, and exit the freeway safely and comfortably. Safety problems can be expected if drivers are forced to reduce speed on the main traffic lanes or to decelerate at a very high rate. In Canada and the United States, the current design guides suggest that operation and safety could be enhanced on freeway SCLs by increasing their length. In this study, driver speed behavior at freeway diverge areas was examined by using data collected on 13 exit ramp terminals on Highway 417 in the city of Ottawa, Canada. The speed, geometric, and traffic data were collected and employed to model 85th percentile speeds and deceleration rates using linear regression analysis. The modeling attempts integrated in this study resulted in eight statistically significant predictive models at the 5% level of significance.

Potential Changes to 2004 Green Book's Adjustment Factors for Entrance and Exit Terminals

AASHTO's Policy on Geometric Design of Highways and Streets (Green Book) notes that acceleration and deceleration lengths should be adjusted on graded ramps. Factors are available in the 2004 Green Book to adjust acceleration lane and deceleration lane lengths for grades of 3% to 6%. The source of the adjustment factors was provided in the 1954 Policies on Geometric Highway Design, in which they first appeared as being based on applying “principles of mechanics to rates of speed change for level grades.” Reviews of this and other documents did not reveal a procedure for determining adjustment factors. A potential source for an adjustment factor for entrance terminals is the calculation of the distance needed to accelerate from one speed to another on different grades by means of vehicle performance equations available in the literature. Potential acceleration length adjustment factors were developed and presented in this paper. The 2004 Green Book provides equations to calculate stopping sight distances for different grades. This methodology was applied to the equations used to calculate deceleration lengths so as to determine deceleration lengths for different grades. The ratio of the deceleration length on a grade to the deceleration length on a level surface formed the basis for adjustment factors for deceleration. Actual performance of vehicles on grades and on a level surface should be measured and compared with the suggested adjustment factors to determine the accuracy of those factors.

Operational and Safety Effects of Right-Turn Deceleration Lanes on Urban and Suburban Arterials

Right-turn deceleration lanes reduce the potential for rear-end collisions from vehicles slowing to make right-turn maneuvers. Right-turn lanes also improve arterial capacity by removing slower-moving vehicles from the main traffic stream. Transportation agencies must have an understanding of the traffic operational and safety effects of right-turn lanes to determine effectively where right-turn lanes are needed. Therefore, in this research, a computer simulation study of motor vehicles and pedestrians at right-turn lanes was conducted to determine their operational effects. A benefit-cost analysis of right-turn lanes that considered both their operational and safety effects was performed. The research indicates that right-turn maneuvers from a two-lane arterial at an unsignalized intersection or driveway can delay through traffic by 0 to 6 s per through vehicle where no right-turn lane is present. Delays to through traffic due to right turns in the same situation on a four-lane arterial are substantially lower, in the range from 0 to 1 s per through vehicle. Pedestrians at unsignalized intersections or driveways can have a substantial impact on delay to through vehicles due to slowing of right-turning vehicles yielding to pedestrians. Provision of a right-turn lane can reduce pedestrian-related delays to through traffic by as much as 6 s per through vehicle, depending on pedestrian volume. Also presented is an economic-analysis procedure that can identify unsignalized intersections and major driveways at which provision of right-turn lanes is cost-effective.

Speed Differential as a Measure to Evaluate the Need for Right-Turn Deceleration Lanes at Unsignalized Intersections

Limited research is available to help transportation agencies make decisions about installing right-turn deceleration lanes at uncontrolled approaches of unsignalized intersections and driveways. Criteria for right-turn lanes developed by some agencies do not adequately consider the effects of through and right-turn movement volumes and speeds. To evaluate the need for right-turn lanes, the percentage of through vehicles behind right-turning vehicles in the outside (right) lane that perform evasive maneuvers because of the presence of right-turning vehicles has been used as a surrogate. This measure is difficult to use under different combinations of volumes, speeds, and other operating conditions; it also cannot be estimated from traffic simulation models if these models are used to evaluate the need for right-turn deceleration lanes. Safety is the most important factor when deciding to provide a deceleration right lane. The speed differential between through vehicles affected by right-turning vehicles and those not affected by these turns is used to determine the need for right-turn deceleration lanes at unsignalized intersections. The speed differential measure has been shown to be a surrogate to safety and to be related to crash involvement. To determine the total speed differential caused by right-turning vehicles in the outside lane, two variables are needed: the number of through vehicles in the outside lane affected by right-turning vehicles and the average drop in speed of affected vehicles. Total speed differential can be used to evaluate the need for a right-turn deceleration lane.

Stop-and-Go Urban Traffic Noise Simulation and Prediction

This paper presents techniques for simulating of urban traffic noise along with a mathematical model of stop-and-go traffic noise for the road network in the city center. The road network in the central part of Bangkok surrounded by the cordon line of Rajchadapisek Ring Road was used as the study area. The analysed data consisted of traffic characteristics and its noise levels which were collected from the study area together with the geometrical dimensions of road sections at each data collection locations. Finally, the stop-and-go traffic noise models generated by this study in the form of acceleration and deceleration lane models, and their statistical goodness of fit tests are presented.

Effects of Access Features and Interaction Among Driveways as Investigated by Simulation

The number, placement, and design features of driveways are important issues in access management. Simulation was used extensively so that the key parameters and variables could be controlled efficiently and so that underlying effects could be studied systematically. Some results were not surprising: deceleration lanes are important, as are acceleration lanes; the presence of driveways has some adverse effect on arterial through-vehicle speed; and the effect is greater as the number of driveways increases. But the emphasis was placed also on the effects on driveway traffic, in terms of driveway per-vehicle delay and queuing. For multiple driveways, the effect on the first (most upstream) driveway of the presence of the others was dramatic. Delay and maximum queue size increased significantly, indicating a substantial reduction in driveway capacity. This reduction was estimated at 30 to 50 percent by an analytic investigation. The effect of adding one downstream driveway was equivalent to increasing the arterial volume by 25 percent in the moderate-to-heavy flow range. Finally, the multiple driveway work revealed an oddity in that the downstream driveway performed better than it would have if it were alone. The authors attribute this to the decreased arterial environment and the “sheltering” effect of the turbulence from the upstream driveway.

A simulation approach for examining capacity and operational performance at freeway diverge areas

Freeway diverge areas, and particularly those in the proximity of exit ramps, are often viewed as potential bottlenecks in freeway operations. The existing diverge procedures within the 1994 and 1997 Highway Capacity Manual updates are limited in that they do not provide a direct estimate of freeway capacity nor do they model performance at oversaturated traffic conditions. Moreover, a parallel investigation on these procedures revealed some inconsistencies in predicting measures of performance at those critical areas. This paper describes the use of computer traffic simulation to explore the patterns of capacity and operational performance behaviour at these areas under the impact of some key geometric and traffic variables. For this purpose, the microscopic traffic simulation model INTEGRATION was selected to conduct an extensive experimental work on a typical ramp-freeway diverge section. Five control variables were investigated, namely, total upstream demand, off-ramp demand, length of deceleration lane, off-ramp free-flow speed, and number of lanes at mainline. The impact of upstream or downstream ramps is considered beyond the scope of this research. Except for off-ramp free-flow speed, the impact of other control variables on capacity and operational performance was shown to be significant. Also, the simulated trends of traffic behaviour showed considerable agreement with logic and expectations in light of the current state of knowledge on freeway operations.Key words: freeways, diverge, capacity, operations, traffic simulation.

Modeling of Urban Area Stop-and-Go Traffic Noise

Simulation of urban traffic noise along with a mathematical model of stop-and-go traffic noise for the road network in the city center is presented in this paper. The road network of the central part of Bangkok surrounded by the Cordon line of Rajchadapisek Ring Road was used as the study area. The analysis data consisted of traffic characteristics and its noise levels, which were collected from the study area. The geometrical dimensions of road section at each data collection location also were measured. Characteristics of traffic noise from different types of vehicles were analyzed, including tuk-tuks (motorized tricycle taxis) and motorcycles, which are considered as popular vehicle types in Bangkok. Characteristics of traffic noise levels and data on other traffic noise parameters were used to analyze and subsequently construct the stop-and-go traffic noise simulation model. Finally, the resultant stop-and-go traffic noise models, which are separated into acceleration and deceleration lane models and ...

Vehicle Behavior on Deceleration Lanes

This paper presents an analysis and evaluation of vehicle flow characteristics on rural deceleration lanes. Site observations were conducted by means of video photography, tape‐switches for transmitting speed information, and, for braking information, by hidden observers. Findings indicated considerable differences between commonly accepted assumptions of the AASHTO model for deceleration lane length determination and actual vehicle behavior. Major points include: (1) Average speeds of diverging vehicles at start of deceleration lanes were lower than average speeds of through vehicles; (2) deceleration values, for deceleration in gear and while braking, were lower than values suggested by AASHTO; and (3) average initial deceleration in gear lasted three times as long as the value currently assumed for design purposes. A model was then formulated to determine deceleration lane length, based on average freeway and exit ramp running speeds.

Design of Acceleration and Deceleration Lanes

Design of Acceleration and Deceleration Lanes