METHOD FOR REGIONAL SYSTEM WIDE OPTIMAL SIGNAL TIMING FOR TRAFFIC CONTROL BASED ON WIRELESS PHONE NETWORKS

• US 20030014180A1
• Filed: 07/10/2001
• Published: 01/16/2003
• Est. Priority Date: 07/10/2001
• Status: Active Grant

• Current Assignee: Makor Issues & Rights Ltd.
• Original Assignee: Makor Issues & Rights Ltd.
• Inventors: Myr, David
• Granted Patent: US 6,539,300 B2
• Time in Patent Office: Days
• US Class Current: 701/117
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions
• CPC Class Codes: G08G 1/081 Plural intersections under common control
• CPC Class Codes: G08G 1/20 Monitoring the location of vehicles belonging to a group, e.g. fleet of vehicles, countable or determined number of vehicles

Abstract

A long-standing problem in traffic control is optimization of the flow of vehicles through a given road network. The present invention describes the network system wide control by means of which real time adjustments of the timings of all signals in a traffic network are made in such a way as to achieve an overall reduction in congestion conditions. First, signals obtained from vehicular-based cellular phones and from GPS based technology whenever available are used for collecting location information on moving vehicles. This location information is obtainable from wireless location systems such as GSM in Europe, CDMA in the USA, or PDC in Japan, and depends on supporting technologies, which are in the process of perpetual improvement. It is further used as an input for an Intelligent Traffic Control System that utilizes the cellular network'"'"'s capabilities to provide sufficiently reliable position information that is stored in the form of records of vehicle phone coordinates, time stamps, etc. Those records together with detailed digital maps are used by mathematical models and algorithms that compute actual travel times consumed by traveling along road sections, by queuing near signalized intersections, and by making various allowed turns and go-throughs in the vicinity of signalized intersection areas. The actual travel times measured for a fixed control time period and reflecting travel congestion, are compared to the corresponding theoretical travel times and form a basis for a certain mathematical optimization model. Maximization of that model allows computation of adjusted phase timings for all signalized intersections within a given area in such a way as to optimize vehicular flows for the next control period and thereby to improve on the congested traffic conditions.

Claims

1. The system for controlling and adjusting phase timings at all signalized intersections within a given geographical region with the purpose of allocating more green light time for roads with heavier traffic flows at the expense of less loaded roadways comprising the steps of:

acquiring of dynamic traffic information from a cellular network provider or a group of cellular network providers and from GPS based technology whenever available for the purpose of monitoring movements of as many traveling vehicles in a given region as possible;

continuously or periodically obtaining location data on plurality of cell phones in the regional network in a specific real time frame;

determining for each particular cell phone whether the cell phone terminal is located in a traveling vehicle;

setting up a list of all cell phones currently identified as located in traveling vehicles;

compiling and updating a sequence of real time positions of each cell phone located in a traveling vehicle;

positioning each cell phone located in a traveling vehicle onto an appropriate road section at each particular moment according to its coordinates;

eliminating untenable cell phone positions (outlying positions) by analyzing series of recently recorded positions and relating them to nearby road sections;

making imputations for missing cell phone positions by analyzing series of recently recorded positions and relating them to nearby road sections;

calculating feasible continuous paths for all cell phones located in traveling vehicles within a given time period;

identifying multiple phones in a common vehicle and combining them into a single vehicular cluster entity based on closely located positions at corresponding time moments and common direction of movement;

calculating feasible continuous paths for vehicular clusters within a given time period;

storing the relevant position data for each individual vehicle (vehicular cluster) traveling along a given road section in the database for the purpose of maintaining vehicle'"'"'s recent path information.

2. The system according to claim 1 for estimating and updating previously computed estimates of travel times for all road sections and of crossing times for all signalized intersections in a given geographical region comprising the steps of:

continuously maintaining and updating for each road section the list of vehicles that recently entered it together with other relevant information;

continuously maintaining and updating for each road section the list of vehicles that recently exited it together with other relevant information;

continuously maintaining and updating at the database the list of vehicles moving within a given geographical region together with other relevant information for each road section;

continuously maintaining and updating for each turn and each go-through of each signalized intersection the list of vehicles that recently passed there together with other relevant information;

computing statistical (e.g. linear regression) estimates of travel times for each road section at each time period;

computing statistical (e.g. linear regression) estimates of crossing times for each turn and each go-through of each signalized intersection at each time period;

continuously maintaining and updating an estimate of averaged recent travel time for each road section;

continuously maintaining and updating an estimate of averaged recent crossing time for each turn and each go-through of each signalized intersection.

3. The system according to claim 1 for estimating and adjusting previously computed green light timings at all signalized intersections in a given geographical region for the next time period comprising the steps of:

maximization (under appropriate restrictions) of a linear objective function in green light timings with the coefficients that measure time delays at all signalized intersections resulting from traffic congestion;

computing the values of green light timing variables that bring the linear objective function to its maximum;

applying the obtained values of green light timing variables to the corresponding signalized intersections for controlling phase timings during the next time period.

4. The system according to claims 1 and 3 for computing the coefficients that enter into the linear objective function and measure time delays at all signalized intersections resulting from traffic congestion at the current time period, comprising the steps of:

computing theoretical travel times for all turns and go-throughs related to the signalized intersections at the current time period within a given region;

estimating actual travel times for all turns and go-throughs related to the signalized intersections at the current time period within a given region by means of solving linear regression equations;

computing the coefficients that enter into the linear objective function and measure time delays as ratios of averaged actual travel times of all turns and go-throughs to the corresponding theoretical travel times;

computing the linear objective function to be maximized by linear programming methods as a function in green light timings with the coefficients that measure time delays.

5. The system according to claims 1 and 2 for storing and updating traffic situations at road sections and signalized intersections in a regional road system comprising the steps of:

maintaining and updating lists of moving vehicles together with other relevant information for road sections;

maintaining and updating lists of vehicles for road sections that recently exited them together with other relevant information;

maintaining and updating estimates of averaged recent travel times for road sections;

maintaining and updating estimates of averaged crossing times for signalized intersections;

estimating and updating the current status of the traffic situation and traffic flow at each road section;

estimating and updating the current status of the traffic situation and traffic flow at each signalized intersection;

calculating turning proportions of vehicles on signalized intersections.

6. The system according to claims 1-2 and 5 for collecting, processing and storing real time traffic data comprising the steps of:

collecting and storing real time road traffic data for various road sections in a given geographical region;

preparing real time road traffic data for various urban geographical regions;

providing the data to various client applications such as on-vehicle navigation systems, Internet based traffic servers, etc.

compiling historical statistical traffic data on road sections and traffic intersections on the hourly, daily, weekly and monthly basis;

compiling short term and long term predictions of traffic volumes and travel times for road sections and traffic intersections.