Abstract:
System for optimal matching of ride sharing requests. A trip request manager receives trip requests from patrons and a shareability network is established. The system checks to see whether certain parameters related to ride-sharing delays are less than or equal to other parameters to decide whether trips are shareable.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a point-to-point ride sharing system that computes in real time optimal matching of ride sharing requests based on a shareability network. 
         [0002]    Analytical and experimental studies based on real-world taxi date sets form different cities in the world (New York, San Francisco, Singapore, and Veinna) have shown a consistent, large potential for taxi ride sharing. In New York, more than 95% of taxi trips can be shared if a maximum delay parameter is set to five minutes, with an operational cost reduction on the order of 30%. Similar results have been obtained in other cities. An operational cost reduction on the order of 30% is very profitable for a taxi company, and allows the definition of a business model in which the benefits of ride sharing are distributed between customers (who pay a lower fare), drivers, and the taxi company itself. 
         [0003]    Although several prior art systems have been introduced for real-time collection of trip requests (e.g., taxi e-haling and booking systems), only some of them consider the possibility of sharing rides among patrons. The common practice for ride sharing is that trip requests are elaborated in a sequential fashion: when a new request R A  from patron A arrives, the request is checked for potential sharing with a pool of existing pending requests; depending on parameters such as pickup/dropoff points, patron profile, etc., some of these requests {R 1 , R 2 , . . . } are considered potentially sharable with R A . The pool {R 1 , R 2 . . . } of potentially sharable rides is returned to patron A who then selects the preferred ride sharing option among them, i.e., the ride sharing decision is left to the patron. This method is highly ineffective since a composition of individual patron decisions is not guaranteed to find the system-wide optimal combination of shared trips—and actually in practice it is very likely to build a highly suboptimal solution. 
         [0004]    An object of the present invention is a methodology in which trip requests are processed in batches instead of sequentially and trip sharing is decided by a centralized server instead of by a composition of individual customer decisions. 
       SUMMARY OF THE INVENTION 
       [0005]    The system according to the invention for optimal matching of ride sharing requests includes a trip request manager module to receive trip requests from patrons and a trip matching manager module to optimally match trip sharing requests from the trip request manager module. A travel time estimation module and a vehicle dispatching module are also provided. The travel time estimation module calculates:
       a. Travel time from P A  to D A  equals TT a      b. Travel time from P i  to D i  equals TT b      c. Travel time from P A  to P i  equals TT c      d. Travel time from D i  to D A  equals TT d      e. Travel time from P i  to D A  equals TT c      f. Travel time from D A  to D i  equals TT f      g. Travel time from P i  to P A  equals TT g      h. Travel time from P A  to D i  equals TT h          
 
         [0014]    wherein P A  is the pickup location for patron A, D A  is the dropoff location for patron A, P i  is the pickup location of patron i and D i  is the dropoff location for patron i; and 
         [0015]    wherein the trip matching manager module computes whether:
       A. (t A +TT c ≦t i +Δ) and (t A +TT c +TT b +TT c ≦t A +TT a +Δ) and (n a +n i ≦C)   B. (t A +TT c +TT c ÷t A +TT a +Δ) and (t A +TT c +TT e +TT f ≦t i +TT b Δ) and (n a +n i ≦C)   C. (t i +TT g ≦t A +Δ) and (t i +TT g +TT a +TT f ≦t i +TT b +Δ) and (n a +n i ≦C)   D. (t i +TT g +TT h ≦t i +TT b +Δ) and (t i +TT g +TT h +TT d ≦t A +TT a +Δ) and (n a +n i ≦C)       
 
         [0020]    wherein if any one of the conditions, A, B, C or D is satisfied, trip requests R A  and R i  are sharable, wherein t A  is a desired pickup time for a patron A, t i  is a desired pickup time of a patron i, n a  is the number of passengers requesting trip A, n i  is the number of passengers requesting trip i, Δ is a delay parameter and C is passenger seating capacity. 
         [0021]    In a preferred embodiment, the trip matching manager module runs a maximum matching algorithm to maximize the number of shared trips. In another embodiment, the trip matching manager is adapted to match more than two shred rides. In yet another embodiment, the trip matching manager module utilizes a maximum weighted matching algorithm to find a collection of shared trips that minimize system operational cost, where the weight assigned to a pair of shareable trips for patrons A and i equals the system operation savings of running a shared trip instead of running the two trips for A and i separately. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0022]      FIG. 1  is a schematic illustration of the ride sharing system according to an embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The present invention enables optimal matching of ride sharing requests in real time. Trip requests issued by patrons using their smart phone or similar mobile device are delivered to a central server. As requests arrive, the server builds and maintains a shareability network that is a mathematical model of sharing opportunities between pairs or triplets of trips. At a prescribed time interval T (e.g., one minute), the central server computes the optimal matching of the trips in the current shareability network, and returns the results of the computation to a vehicle dispatching system. The vehicle dispatching system decides the assignment of available vehicles to shared trip requests and notifies the patrons of estimated pickup time and notifies vehicle drivers (or onboard self-driving systems) to pick up the prescribed patrons. 
         [0024]    The architecture of an embodiment of the invention is shown in  FIG. 1 . The system of the invention comprises the following components: a mobile device (smart phone, tablet or similar device) by means of which a patron can interact with a transportation provider; a transportation service system (TSS) operated by a point-to-point transportation provider; and a fleet of vehicles servicing the mobility demand of patrons. These three components communicate with one another by means of wireless communication such as cellular, WiFi or the like. With reference to  FIG. 1 , the transportation service system (TSS)  10  includes a trip request manager module (TRM)  12  that collects and responds to patron requests. The request from the TRM  12  is delivered to a trip matching manager module (TMM)  14  that optimally matches trip sharing requests according to the shareability network methodology to be described below. The TMM  14  communicates with a travel time estimation system (TTES)  16  that is used to build and maintain the shareability network. A vehicle dispatching system (VDS)  18  dispatches vehicles  20  to service the trip requests. 
         [0025]    Still referring to  FIG. 1 , a patron A accesses the point-to-point transportation application on his or her mobile device  22  and requests a trip by issuing a trip request R A . The trip is specified by including in the request a pickup location P A  (which can be derived from the GPS of the mobile device  22 ), a dropoff location D A  (e.g., an address), the desired pickup time t A , and the number n A  of passengers requesting the trip. The application offers the patron the possibility of requesting a shared trip which can be done by pressing a suitable button in the app GUI. The patron is informed by the application that he or she will receive a response from the system within a time T, where T is a system parameter chosen by the transportation service provider. Whether the requested trip is shareable is indicated in the trip request through a sharability field S A  set to 1 if the trip is shareable, and set to 0 otherwise. The trip request is transmitted to the TSS  10  by means of wireless communication, e.g., using an available cellular or WiFi connection. 
         [0026]    The trip request is received by the TRM  12  and forwarded to the TMM  14  when the shareability field S A  in the request is set to 1. If there is to be no ride sharing, the request is merely forwarded directly to the VDS  18  for vehicle  20  dispatch. 
         [0027]    The TMM  14  builds and maintains a data structure called a shareability network. The data structure contains one element for each active request, where the set R equals {R 1 , R 2 , . . . } of active requests is defined to be the set of requests for which trip matching and vehicle dispatching has not yet been defined. Furthermore, the element corresponding to request R i  in the data structure contains the number of passengers n i  in the request and a reference to the elements of the data structure corresponding to a set of shareable requests R j , R k , . . . , which is defined as the subset of R comprised of all and only the requests in R that can be shared with R i . Sharability between trips is determined according to the following procedure. 
         [0028]    When a new request R A  arrives from the TRM  12 , a new element corresponding to R A  is built in the shareability network. Furthermore, each request R i  in R is considered. If said R is empty then R is set to R={R A }. If R is not empty, for each considered request R i  the TMM  14  determines whether R A  and R i  can be shared according to the following method. Let P A , D A , P i , D i  be the pickup and dropoff locations of the two trips. Let t A , t i , be the respective desired pickup times and let n A , n i  be the respective number of passengers. The TMM  14  interrogates the TTES  16  requesting computation of the following travel times:
       a. From P A  to D A      b. From P i  to D i      c. From P A  to P i      d. From D i  to D A      e. From P i  to D A      f. From D A  to D i      g. From P i  to P A      h. From P A  to D i .       
 
         [0037]    The TTES  16  responds to the TMM  14  sending a list of estimated travel times, called TT a , TT b , TT h —each referring to the start/ending point of the travel. 
         [0038]    The TMM  14  receives the estimated travel times TT a , TT b , . . . , TT h  and performs the following actions, where Δ is a predefined system parameter called the delay parameter and C is a predefined system parameter called the vehicle passenger seating capacity. 
         [0039]    The system checks whether
       A. (t A +TT c ≦t i +Δ) and (t A +TT c +TT b +TT d ≦t A +TT a +Δ) and (n a +n i ≦C)   B. (t A +TT c +TT e ≦t A +TT a +Δ) and (t A +TT c +TT e +TT f ≦t i +TT b +Δ) and (n a +n i ≦C)   C. (t i +TT g ≦t A +Δ) and (t i +TT g +TT a +TT f ≦t i +TT b +Δ) and (n a +n i ≦C)   D. (t i +TT g +TT h ≦t i +TT b +Δ) and (t i +TT g +TT h +TT d ≦t A +TT a +Δ) and (n a +n i ≦C)       
 
         [0044]    If any one of the conditions A, B, C, D is satisfied, trip requests R A  and R i  are considered shareable. In such case, a reference to the element of the shareability network corresponding to trip R i  is included with the element corresponding to trip R A , and vice versa. The data structure also records in the elements corresponding to R A  and R i  which of the conditions A, B, C, D for shareability of requests R A  and R i  were satisfied. This is called route information. No action is undertaken otherwise, i.e., in case the two trips cannot be shared. 
         [0045]    Every T seconds, where T is the system parameter discussed above, the TMM  14  runs a maximum matching algorithm on the graph uniquely defined by the reference between nodes m the shareability network. The matching algorithm guarantees maximization of the number of shared trips. As a result of this computation, the set of requests in R is partitioned into a set R M  of matched, requests, and into a set R NM  of non-matched requests. Requests in R M  are organized in pairs representing shared trips as defined by the maximum matching algorithm. For each pair (R i , R j ) of requests in R M , a shared trip request is prepared and forwarded, to the VDS  18 . The shared trip request contains P A , D A , t A , P i , D i , t i , as well as die routing information that has been stored in the shareability network. After the shared trip request is prepared, both the elements corresponding to R i  and R j  in the shareability network are deleted along with, corresponding references to R i , R j  in other elements of the data structure. Non-matched requests R NM  are forwarded to the VDS  18  as simple trip requests, The simple trip request corresponding to request R h  reports the following information: P h , D h , t h . After the trip request is prepared, the element corresponding to R h  in the shareability network is deleted, along with the corresponding references to R h  in other elements of the data structure. 
         [0046]    The VDS  18  receives trip requests either from the TMM  14  or from the TRM  12 , Trip requests can be either simple or shared and are processed sequentially. When processing a request, the VDS  18  determines which vehicle  20  should serve the request according to a vehicle dispatching algorithm. Furthermore, the estimated pickup time at the patron&#39;s location is computed. In case of a shared trip request, pickup times at both patrons&#39; locations are estimated based on the route information. The VDS  18  informs the TRM  12  of the estimated patrons&#39; pickup time(s). 
         [0047]    The VDS  18  informs the vehicle  20  of the trip request and of the corresponding pickup location via wireless communication. In ease of a shared trip request, the vehicle is informed of the pickup locations of both patrons, and which of the two patrons should be picked up first. The TRM  12  then informs the patrons of the estimated pickup time(s). Thereafter, die vehicle picks up the patrons. 
         [0048]    The above described system can he extended to consider sharing of up to three trips or even larger number of shared trips. The output, of the TMM  14  may utilize a maximum weighted matching algorithm to find die collection of shared trips that minimizes system operational cost. 
         [0049]    As an optional matter, a patron can be presented with three estimated fares for the requested trip: a fare F 1  in case he or she opts for the no sharing option, a fare F 2  in case he or she opts for the sharing option but the trip could not be shared, and a fare F 3  in the case that a trip is shared. The fares are designed in such a way that F 3  is less than or equal to F 2  less than or equal to F 1 . 
         [0050]    It is thus seen that trip requests in the present system are processed in batches instead of sequentially as known on the prior art. Further, trip sharing is decided by a centralized server instead of by a composition of individual customer decisions. The invention implements a methodology for computing optimal matching of trips—defined according to a clearly specified parameter—in real-time. Experiments we have performed have shown that the approach disclosed herein can find the optimal matching of as many as 10,000 trips in less than 0.01 seconds when a computer program that matches the trips is executed on a standard Linux server. 
         [0051]    Those of ordinary skill in the art will recognize that the present invention can be used to implement a ride-sharing taxi system. Other applications include dynamic, on-demand “flexibus” systems in which a fleet of minivans with moderate seating capacity such as nine seats are used to provide point-to-point transportation to individuals or small groups. More broadly, the present invention can be used to implement any transportation system providing point-to-point transportation for individuals or small groups. 
         [0052]    It is recognized that modifications and variations of the present invention will be apparent to those of ordinary skill in the art and it is intended that all such modifications and variations be included within the scope of the appended claims.