Implementation of a Double Continuous Flow Intersection in Riyadh

The continuous growth of population in the capital, coupled with increased auto ownership and dependence has worsened traffic conditions on Riyadh's road network. Conventional methods to address this increased demand could be costly and insufficient. There has been greater interest in using alternative measures to improve the performance and safety characteristics on main corridors, particularly those that arrive at signalized intersections. Heavy left turning traffic at these intersections is one of the main causes for delays. Previous research has investigated several types of alternative designs termed "unconventional" arterial intersection designs that could minimize the effect of left turning traffic. This paper provides decision makers with an objective assessment on the efficiency of implementing an unconventional intersection design, the Double Continuous Flow Intersection (DCFI) configuration, to improve the operational and safety characteristics of an existing major signalized arterial intersection in Saudi Arabia. In this study, the Kingdom Hospital Intersection in Riyadh was selected, as it is one of the most congested intersections in Riyadh. Using the collected traffic data, the micro-simulation program VISSIM was used to analyze and compare the efficiency of both configurations. When compared to the existing conventional signalized intersection design, it was found that the proposed Double Continuous Flow Intersection (DCFI) unconventional intersection design decreased the average delay per vehicle by 99 seconds. The proposed Double Continuous Flow Intersection configuration also improved the Level of Service at the intersection from level F (152 sec/veh average delay) to level D (53 sec/veh average delay).

Developing Signal Warrants for Restricted Crossing U-Turn Intersections

The restricted crossing U-turn (RCUT) intersection is a form of innovative intersection design that reroutes left-turn and through traffic from the minor road to U-turn crossovers on the major road. When implemented correctly, an RCUT intersection can provide significant safety and operational benefits over the conventional intersection configuration. The RCUT may be controlled by traffic signals, STOP control, merges and diverges, or a combination of these. There is currently no concrete guidance in relation to when the use of traffic signal control is warranted at an RCUT intersection. This study investigated traffic volume conditions that may warrant consideration of traffic signal control at an RCUT intersection. Simulation experiments including two geometric configurations and three traffic control schemes were designed and run in VISSIM to evaluate the effects of traffic conditions on intersection delay and queue lengths. Traffic was varied by changing the composition, approach volumes, and origin–destination flow patterns to reflect different conditions that may occur at the intersection on any given day. For the range of conditions studied, the results of the simulation analysis suggested that the RCUT intersection may operate better with traffic signals (at all junctions) when the minor roadway traffic volume is more than 450 vehicles per hour (vph) and the major roadway has two through lanes. The corresponding minor roadway volume threshold increases to 575 vph when the major roadway has four through lanes.

NUMBER OF CONFLICTS AT THE ROUTE INTERSECTION – MINIMUM DISTANCE MODEL

A conflict is an infringement of minimum separation between at least two aircraft. The model is based on these assumptions: aircraft fly on level straight line routes, only an infringement of the lateral separation is considered, deviations are excluded, aircraft at the same flight level fly the same average speed, and aircraft fly towards an intersection and may change direction after intersection. Hence, conflicts mainly occur owing to a loss of minimum separation between aircraft flying at the same flight level. Calculation of average number of potential conflicts is designated for long time interval; hence, aircraft velocity deviations are negligible. The mathematical model in this paper is intended to compare different alternatives of intersection configuration of air traffic services routes. The comparison is based on the results: an average number of potential conflicts per hour on intersection of routes, index of conflicts intensity, and intersection capacity.

Ruled Exceptional Surfaces and the Poles of Motivic Zeta Functions

In this paper we study ruled surfaces which appear as exceptional surface in a succession of blowing-ups. In particular we prove that the e-invariant of such a ruled exceptional surface E is strictly positive whenever its intersection with the other exceptional surfaces does not contain a fiber (of E). This fact immediately enables us to resolve an open problem concerning an intersection configuration on such a ruled exceptional surface consisting of three nonintersecting sections. In the second part of the paper we apply the non-vanishing of e to the study of the poles of the well-known topological, Hodge and motivic zeta functions.

Benefits of Split Intersections

As urban and suburban intersections become more congested, a likely remedy for recurring traffic jams is grade separation in the form of diamond or tight diamond interchanges. A more economical intersection configuration to relieve congestion has been built overseas. The major highway is separated into two-directional, one-way roads comparable to an at-grade diamond junction known as the split intersection. The split intersection facilitates smoother flows with less driver delay, mainly by reducing the number of required signal phases from four to three. The success of converting to the split intersection has been analyzed by using deterministic methods that showed increased capacity and noticeable reduction in delay. The analysis methodology relies on a microsimulation technique to predicate previous claims and provide economic benefits. Comparisons of vehicular delay between the single and the split intersection revealed substantial savings in travel delay, particularly for higher entering volumes and higher left-turning movements. The findings provide guidance to planners and designers on the expected benefits of converting a four-lane by four-lane single intersection to the split intersection.