TRAFFIC OPTIMISATION BY CLOVERLEAF INTERCHNGES

by RCE Roorkee Roorkee College of Engineering

Cloverleaf is four-leg interchanges that employ loop ramps to accommodate left-turning movements. Interchanges with loops in all four quadrants are referred to as “full cloverleafs” and all others are referred to as “partial cloverleaf”. A full cloverleaf may not be warranted at major-minor crossings where, with the provision of only two loops, freedom of movement for traffic on the major roadway can be maintained by confining the direct at grade left turns to the minor roadway. Comfort and safety are two primary goals of transportation engineering. The number of vehicles is increasing day by day in INDIA. However, no new road is almost constructed for the existing traffic. Therefore, current networks become insufficient. Constructing new road is not economical, so the investor organization tries to improve the road geometries. For this improvement, the parameters of delay and travel time are used for evaluation criteria.

Urban interchanges contain both saturated traffic flow and unsaturated traffic flow. Their traffic characteristics are significantly different from signalized intersections. Traffic flow at urban interchanges is unique; combining actual data and calibration, researchers used the VISSIM simulation model to calculate the capacity of the cloverleaf intersection that has to be made over NH-8. The capacity of the whole interchanges is analyzed by simulation experiments and the relationship between the whole interchanges capacity and turning vehicles proportion is put forward; with an increase of turning vehicles proportions, the whole traffic capacity of the interchanges decreases constantly.

The Southern Peripheral Road (SPR) originates from Gurgaon-Faridabad Road near Ghata and meets NH-8 near kherki Daula, and is proposed to be connected to NPR through CPR. The Central Peripheral Road (CPR) starts from a place close to kherki Daula village and meets NPR near Harbaru village. Construction of SPR is nearing completion, it is already connected with NH-8. Land acquisition for CPR is in advance stage. This has necessitated the construction of an intersection to avoid traffic jams on NH-8, once SPR and CPR get operational. “For smooth traffic flow, a cloverleaf intersection has become essential at the junction of SPR, CPR and NH-8, and reduce traffic on NH-8.

The ultimate objective of grade separated intersection is to climate all grades crossings conflict and to accommodate other intersection maneuvers by merging, diverging and weaving at the low relative speed. Cloverleaf interchanges also provide more acceleration and deceleration space on the freeway and to go left ( in right-hand traffic) vehicles first continue as one read passes over or under the other, then exit right onto a one-way three-fourth loop ramp and merge onto the intersecting road.It maintains a continuing program of highway system study and improvement. Interchanges areas that have been recently studied as part of a pre-engineering report, programmed for improvement (regardless of the design stages), recently improved or are under construction do not require independent evaluation. These interchanges did not receive a full evaluation in this study. A total of 132 interchanges locations were identified as recently studied or constructed and are identified as “Recent Activity” interchanges. To provide the most cost-effective planning effort, each existing interchanges location was reviewed.

The accident rate was calculated for each interchange based on the accident severity divided by the total number of existing vehicles entering an interchanging on a daily basis. Although the total number and severity of accidents occurring at interchanges is an important factor in the comparison of the need for the interchanges improvement, the accident rate is an indicator of performance related to total traffic volumes. For example, one interchanges may have twice as many accidents as another interchange, but if the traffic volumes are also twice as much, the interchanges are equal relative to the performance measured by accidents per 1,00,000 vehicles entering the interchanges. In itself, the estimated future traffic volume entering an interchanging is not a measure of deficiency or performance. It is, however, an indicator of exposure of interchanges deficiencies to highway users. For example, the same poor level-of-service at an interchanges intersection would have a greater cumulative impact on the user at an interchange with 2,00,000 daily entering vehicles compared to an interchange with only 5,00,000 daily vehicles. In other words, total vehicles delay would be greater at the higher volume interchanges. Any interchanges deficiencies would be experienced by a greater or lesser number of users depending on the total number of vehicles traversing the interchanges. Therefore, this factor is a measure of daily “exposure” to the interchanges conditions.

Conclusion: Micro-simulation models are developed to study the impact of configuration changes to a cloverleaf near metropolitan city limits in India. Different designs that incorporate variables that traffic volumes are investigated in this study. The evaluation of alternatives is limited to few configurations, while several others those are equally viable and optimum are possible. Research suggests that low traffic volumes improve the traffic condition of a full cloverleaf configuration and reduces environmental impacts. The alternative configurations tested resulted in minimal changes to travel time. For medium traffic volumes, an improvement is seen with every alternatives configuration that is checked. The best ranking alternatives are the alternatives which included increases in lanes. It is bottlenecked in the network and provided for enough storages space in turning pockets and to reduces the queue spillback that will occur on the mainlines.

PREPARED BY: -

REETA JOSHI (CIVIL ENGINEERING DEPARTMENT)

ROORKEE COLLEGE OF ENGINEERING