Evaluation of safety and operational impacts of bicycle bypass lanes at modern roundabouts

2008 ◽  
Vol 35 (10) ◽  
pp. 1025-1032 ◽  
Author(s):  
Essam Dabbour ◽  
Said M. Easa
Keyword(s):  
Traffic Signals ◽  
Signalized Intersections ◽  
Vision Impairment ◽  
Evaluation Scheme ◽  
Pedestrian Traffic ◽  
Negative Impacts ◽  
Operational Impacts ◽  
Full Utilization

Modern roundabouts have been found to improve safety and reduce overall delay, but they may have negative impacts on the safety of cyclists as other vehicles may cut-off cyclist paths while entering or exiting the roundabout. Several before–after studies have found an increase in traffic collisions involving cyclists at roundabouts after being converted from conventional signalized intersections. Another concern associated with roundabouts is the safety of pedestrians, especially pedestrians with severe vision impairment who may find difficulty in negotiating roundabouts. This paper evaluates safety and operational impacts of using bicycle bypass lanes at roundabouts as a means of increasing the safety of cyclists. The paper also recommends the full utilization of pedestrian traffic signals, proposed by other studies, by incorporating them with the proposed bicycle bypass lanes. An evaluation scheme involving the safety benefits and the costs of the proposed bypass lanes is provided to help practitioners decide when they are warranted. The evaluation scheme is illustrated using an application example.

Validation of Generalized Delay Model for Vehicle-Actuated Traffic Signals

1997 ◽  
Vol 1572 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Nagui M. Rouphail ◽  
Mohammad Anwar ◽  
Daniel B. Fambro ◽  
Paul Sloup ◽  
Cesar E. Perez
Keyword(s):  
North Carolina ◽  
Field Data ◽  
Traffic Signals ◽  
Signalized Intersections ◽  
Delay Model ◽  
Highway Capacity ◽  
Generalized Model ◽  
Highway Capacity Manual ◽  
Traffic Volumes ◽  
Isolated Intersection

One limitation of the Highway Capacity Manual (HCM) model for estimating delay at signalized intersections is its inadequate treatment of vehicle-actuated traffic signals. For example, the current delay model uses a single adjustment for all types of actuated control and is not sensitive to changes in actuated controller settings. The objective in this paper was to use TRAF-NETSIM and field data to evaluate a generalized delay model developed to overcome some of these deficiencies. NETSIM was used to estimate delay at an isolated intersection under actuated control, and the delay values obtained from NETSIM were then compared with those estimated by the generalized delay model. In addition, field data were collected from sites in North Carolina, and delays observed in the field were compared with those estimated by the generalized delay model. The delays estimated by the generalized model were comparable with the delays estimated by NETSIM. The data compared favorably for degrees of saturation of less than 0.8. However, at higher degrees of saturation, the generalized model produced delays that were higher than NETSIM’s. Some possible explanations for this discrepancy are discussed. The delays estimated by the generalized model were comparable with delays observed in the field. Researchers have concluded that the generalized delay model is sensitive to changes in traffic volumes and vehicle-actuated controller settings and that the generalized delay model is much improved over the current HCM model in estimating delay at vehicle-actuated traffic signals.

Pedestrian Travel Times and Motor Vehicle Traffic Signals

1996 ◽  
Vol 1553 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Robert B. Noland
Keyword(s):  
Travel Time ◽  
Motor Vehicle ◽  
Traffic Signals ◽  
Vehicle Traffic ◽  
Cycle Times ◽  
Signal Average ◽  
Vehicle Delay ◽  
Pedestrian Traffic ◽  
Pedestrian Travel ◽  
Travel Delay

Traffic signals generally have been installed to maximize the flow of motor vehicle traffic by reducing the average travel delay time. Under free-flow conditions, motor vehicle travel delay is very sensitive to the amount of green phase and the total cycle of the traffic signal. Average pedestrian delay at traffic signals is not taken into account. Some simple examples are used to demonstrate that travel time delay costs to pedestrians caused by existing signalization cycles may often result in increased travel time costs to society. In areas with heavy pedestrian traffic (or during peak pedestrian hours), traffic signals should trade off the costs of motor vehicle delay with pedestrian delay. This may suggest that in some areas, motor vehicle traffic should be banned or severely restricted. Narrower street widths that can allow reduced total signal cycle times can also reduce pedestrian delay.

Effect of Bicycles on Capacity of Signalized Intersections

1998 ◽  
Vol 1646 (1) ◽  
pp. 87-95 ◽  
Author(s):  
D. Patrick Allen ◽  
Joseph E. Hummer ◽  
Nagui M. Rouphail ◽  
Joseph S. Milazzo
Keyword(s):  
Signalized Intersections ◽  
Signalized Intersection ◽  
Motor Vehicles ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Flow Adjustment ◽  
Conflict Zone ◽  
Pedestrian Traffic ◽  
Saturation Flow ◽  
The Impact

Although much is known about the operation of signalized intersections, little or no empirical research has been conducted regarding the effect of bicycles on signalized intersection capacity. The purpose of this study was to accurately quantify the effects of bicycles on signalized intersection capacity through the videotaping of several intersections that had significant bicycle traffic. Through the videotaping of intersections in Davis, California, and Gainesville, Florida, a relationship was determined between bicycle volumes and the percent of the green phase during which bicycle traffic occupies a conflict zone between bicycles and right-turning motor vehicles. It was also determined that one can ascertain the total net occupancy due to pedestrians and bicycles by taking the overlapping effects between bicycles and pedestrians into account. Using this total occupancy due to bicycles and pedestrians, one can calculate a saturation flow adjustment factor ( fRph) that reflects the reduction in saturation flow, and ultimately lane group capacity, for lane groups containing vehicles making permissive right turns in the presence of bicycles and pedestrians. The proposed procedure yields lower saturation flows and capacities than the current Highway Capacity Manual (HCM) procedure. In other words, on the basis of empirical data, when combined with pedestrian effects, the impact of bicycles on the saturation flow of lane groups containing right-turning vehicles is probably more detrimental than previously believed, and the capacities of intersections with significant bicycle and pedestrian traffic may be overestimated by using the current HCM procedures.

scholarly journals Recognition distance of pedestrian traffic signals by individuals with low vision

2006 ◽  
Vol 43 (6) ◽  
pp. 771 ◽  
Author(s):  
Michael D. Williams ◽  
Ron Van Houten ◽  
Bruce B. Blasch
Keyword(s):  
Low Vision ◽  
Traffic Signals ◽  
Pedestrian Traffic

scholarly journals Integrating Data Mining and Microsimulation Modelling to Reduce Traffic Congestion: A Case Study of Signalized Intersections in Dhaka, Bangladesh

Urban Science ◽  
2019 ◽  
Vol 3 (2) ◽  
pp. 41 ◽  
Author(s):  
S.M. Labib ◽  
Hossain Mohiuddin ◽  
Irfan Mohammad Al Hasib ◽  
Shariful Hasnine Sabuj ◽  
Shrabanti Hira
Keyword(s):  
Data Mining ◽  
Traffic Congestion ◽  
Traffic Signals ◽  
Fixed Time ◽  
Travel Speed ◽  
Signalized Intersections ◽  
Signal Timing ◽  
Data Set ◽  
Video Footage ◽  
Transportation Technologies

A growing body of research has applied intelligent transportation technologies to reduce traffic congestion at signalized intersections. However, most of these studies have not considered the systematic integration of traffic data collection methods when simulating optimum signal timing. The present study developed a three-part system to create optimized variable signal timing profiles for a congested intersection in Dhaka, regulated by fixed-time traffic signals. Video footage of traffic from the studied intersection was analyzed using a computer vision tool that extracted traffic flow data. The data underwent a further data-mining process, resulting in greater than 90% data accuracy. The final data set was then analyzed by a local traffic expert. Two hybrid scenarios based on the data and the expert’s input were created and simulated at the micro level. The resultant, custom, variable timing profiles for the traffic signals yielded a 40% reduction in vehicle queue length, increases in average travel speed, and a significant overall reduction in traffic congestion.

Operational Impacts of Protected-Permitted Right-Turn Phasing and Pavement Markings on Bicyclist Performance during Conflicts with Right-Turning Vehicles

2019 ◽  
Vol 2673 (4) ◽  
pp. 789-799
Author(s):  
Masoud Ghodrat Abadi ◽  
David S. Hurwitz
Keyword(s):  
Traffic Control ◽  
Safety Concern ◽  
Lateral Position ◽  
Signalized Intersections ◽  
Pavement Markings ◽  
Conflict Area ◽  
Flashing Yellow Arrow ◽  
Mixed Factorial Design ◽  
Operational Impacts ◽  
Yellow Arrow

Conflict between bicycles and right-turning vehicles on the approach to signalized intersections is a critical safety concern. To understand the operational implications of protected-permitted right-turn signal indications in conjunction with pavement markings on bicyclist performance, a full-scale bicycling simulator experiment was performed. Velocity and lateral position of bicyclists were evaluated during conflicts between bicycles and right-turning vehicles. A mixed factorial design was considered. Two within-subject factors were analyzed: the signal indication for right-turning vehicles with five levels (circular red, circular green, solid red arrow, solid green arrow, and flashing yellow arrow), and the pavement markings in the conflict area with two levels (white lane markings with no supplemental pavement color and white lane markings with solid green pavement applied in the conflict area). Additionally, the influence of gender as a between-subject variable was considered. Forty-eight participants (24 female) completed the experiment. Signal indications and pavement markings had statistically significant effects on bicyclist velocity and lateral position, but these effects varied at different factor levels. Additionally, during the conflicts, male participants were found to have higher velocity than female participants. This difference was not influenced by engineering treatments. The results provide guidance to transportation professionals about how traffic control devices could be applied to conflict areas on the approach to signalized intersections.

scholarly journals A NEW DELAY PARAMETER DEPENDENT ON VARIABLE ANALYSIS PERIODS AT SIGNALIZED INTERSECTIONS. PART 1: MODEL DEVELOPMENT

Transport ◽  
2008 ◽  
Vol 23 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Ali Payidar Akgüngör
Keyword(s):  
Model Development ◽  
Traffic Signals ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Delay Model ◽  
Delay Models ◽  
Dependent Model ◽  
New Formulation ◽  
Parameter Dependent

Delay is an important factor in the optimization of traffic signals and the determination of the level of service of a signalized intersection. This paper proposes a methodology and a new formulation to identify the delay parameter in signalized intersection delay models. In this study, the delay parameter is modeled as a function of analysis period instead of a fixed value used by the existing delay models. Therefore, the proposed delay model including new delay parameter can produce more reasonable delay estimations at signalized intersections for variable time periods. A comparative study of the proposed time‐dependent model against the existing four different models was performed to present the improvements in this model.

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