Abstract:
A system and method is provided for metering vehicular traffic. Specifically, the system uses a computer to prevent delays as vehicles transition from a greater number of toll lanes to a lesser number of travel lanes. Toll collection devices are used to send a ready signal to a computer to indicate a vehicle is ready to leave a start point. The computer receives ready signals from the toll collection devices and uses a pre-programmed departure schedule to queue the vehicles. After the vehicles are queued, the computer uses time delay variables to ensure efficient traffic flow between the toll lanes of the plaza and the travel lanes of the bridge or tunnel. An indicator signal responsive to a departure signal sent by the computer is employed to direct vehicles from a start point towards a travel lane.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains generally to systems and methods for metering vehicular traffic. More particularly, the present invention pertains to systems and methods for metering the movements of vehicles from respective start points in a plurality of traffic lanes into a common travel lane. The present invention is particularly, but not exclusively, useful as a system and method for metering vehicular traffic moving through multi-lane toll plazas at the entrance to bridges or tunnels. 
       BACKGROUND OF THE INVENTION 
       [0002]    Typically, a toll plaza at the entrance to a tunnel or bridge is laid out with multiple toll booths. If so, each toll booth will service a separate lane, from which access to the bridge or tunnel is granted upon payment of a toll. In most cases, the number of toll lanes will significantly exceed the number of lanes available for travel across the bridge or through the tunnel. When traffic is heavy, the main area for “bottlenecks” causing significant traffic delays is between the toll booth and the bridge or tunnel, in an area that is generally referred to as a departure transition zone. Vehicles moving from the departure transition zone toward the bridge or tunnel are unable to merge smoothly if drivers erratically change speeds or aggressively change lanes. Instead, due to these improper driving techniques, drivers often block multiple lanes of traffic or cause accidents that result in further delays. Even without accidents, the theoretical capacity of the bridge or tunnel is significantly reduced because of the tremendous friction produced by the irregular flow of vehicles. 
         [0003]    In light of the above, it is an object of the present invention to provide systems and methods for metering the flow of traffic through a toll plaza that effectively maintains a steady flow of traffic through the departure transition zone as the number of same-way traffic lanes is significantly reduced. Another object of the present invention is to improve efficiency by increasing the volumetric flow rate of vehicles passing through the bridge or tunnel. A further object of the present invention is to provide a system and method for controlling vehicular traffic that is easy to implement, is simple to use, and is comparatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0004]    In accordance with the present invention, systems and methods for metering vehicular traffic at a toll plaza are provided for the purpose of avoiding congestion in an area between the toll lanes of the toll plaza and the travel lanes of a bridge or tunnel. This area is commonly referred to as a departure transition zone. In particular, the systems and methods of the present invention pertain to vehicles at a plurality of start points moving into the travel lanes of a bridge or tunnel. For the purposes of the present invention, the start point is the location where a vehicle waits after paying a toll and before moving into the departure transition zone. Generally, the start point is the same location where the toll is paid and will be delineated by lines painted on the pavement and a barrier gate. For purposes of the present invention, the plurality of start points will be subdivided into groupings called zones, with a Zone A being the inner toll lanes with the shortest straight-line distance to the travel lanes and a Zone B being the outer toll lanes with the longer distance to the travel lanes. Additional zones can be added as needed to more effectively manage traffic flow. Furthermore, the number of travel lanes per zone will vary based on the individual characteristics of each toll plaza. Essentially, the systems and methods of the present invention require the concerted implementation of three components. These are: 1) a toll collection device to generate a ready signal for the vehicle at the start point, 2) a computer system responsive to the ready signal to establish a “go” signal for the vehicle in accordance with a pre-programmed departure schedule, and 3) an indicator to initiate vehicle movement from the start point into the departure transition zone. 
         [0005]    Structurally, the system of the present invention includes a toll collection device positioned at each start point. The toll collection device can be of any type well-known in the pertinent art. As indicated above, the purpose of the toll collection device is to validate payment, and to create a ready signal. This ready signal will then electronically notify the computer that a vehicle is available to be assigned a position in a queue for entering the travel lane. Specifically, after the computer receives the ready signal, the computer places the vehicle into the queue for entering the travel lane in accordance with the pre-programmed departure schedule. Furthermore, the system includes an indicator in the form of a red “stop” light and a green “go” light. The red “stop” light provides a visual signal to direct the vehicle to wait at the start point while the green “go” light provides a visual signal to direct the vehicle from the start point and into the departure transition zone. 
         [0006]    Functionally, the system of the present invention utilizes the computer to respond to ready signals from the plurality of start points. Upon arrival at the start point, the vehicle pays the toll, and the toll collection device validates the payment and sends a ready signal to the computer. When the ready signal is received, the computer uses the pre-programmed departure schedule to queue the vehicle for entry into the travel lane. Throughout the process, continuous updates are made to the queue as vehicles enter the departure transition zone and other vehicles arrive at the start points. As soon as the computer determines the vehicle can proceed into the departure transition zone, an electronic departure signal is sent directing the indicator positioned at the start point to display the “go” signal. 
         [0007]    In order to ensure unimpeded movement through the departure transition zone, the pre-programmed departure schedule assigns each vehicle in the queue a unique departure time. In addition to its own place in the queue, the other factors used to set the departure time for the vehicle waiting at the start point are the departure time of the previously released vehicle and its departure zone. When the previously released vehicle is from the same zone as the next vehicle in the queue, the computer uses a first time delay to establish the departure time for the next vehicle in queue and to ensure adequate spacing. When the previously released vehicle is from a different zone, the computer will use a second time delay to ensure adequate spacing. The reason for the two distinct time delay values is to account for the greater time taken by a vehicle leaving from Zone B (outer toll lanes) to reach the travel lanes of the tunnel or bridge as compared to a vehicle leaving from Zone A (inner toll lanes). The use of time delay variables ensures vehicles enter the departure transition zone only after the previously released vehicle has moved close enough to the travel lanes so the two vehicles will not impede each other&#39;s movement and cause a delay. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
           [0009]      FIG. 1  is a schematic of a toll plaza; 
           [0010]      FIG. 2  is a schematic showing the inter-relationships of components for the present invention at the toll plaza; and 
           [0011]      FIG. 3  is a logic chart showing the operation of “stop” and “go” signals at a start point in the toll plaza. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0012]    Referring initially to  FIG. 1 , a layout for metering traffic in accordance with the present invention is shown and generally designated  10 . An exemplary toll plaza within the layout  10  where traffic is metered in accordance with the present invention is schematically shown and is designated  12 . As shown, the toll plaza  12  is divided into two zones: a Zone A that includes toll lanes  14   a - d,  and a Zone B that includes toll lanes  14   e - g.  In the toll plaza  12  shown, each toll lane  14   a - g  has an associated start point  16   a - g.  In this exemplary illustration, seven toll lanes  14   a - g  feed into a single travel lane  18 . Between the toll lanes  14   a - g  and the travel lane  18 , the toll plaza  12  establishes a departure transition zone  20  where the seven toll lanes  14   a - g  transition to the single travel lane  18 . As illustrated, a vehicle  22   c  in toll lane  14   e  of Zone B has a greater distance to travel from its start point  16   e  to reach the travel lane  18  than does a vehicle  22   a  in toll lane  14   a  of Zone A. For illustrative purposes, the exemplary toll plaza  12  consists of seven start points  16   a - g  and seven associated toll lanes  14   a - g.  Actual control of vehicles  22   a - d  through the departure transition zone  20  requires a computer  24  (see  FIG. 2 ). 
         [0013]      FIG. 2  shows the relative location of the components at the toll plaza  12 . Notably, the computer  24  is housed in a central location and is electronically connected to each start point  16   a - e.  Furthermore, each start point  16   a - e  has a respective indicator  26   a - e  and a respective toll collection device  28   a - e.  In an alternate embodiment, each start point  16   a - e  may also have a sensor  30   a - e  in the form of an inductive coil embedded in the pavement (not shown). Preferably, each sensor  30   a - e  is a pneumatic tube laid across the lanes, or any other type sensor well-known in the pertinent art. For the purposes of the present invention, the sensor  30   a - e  verifies when a vehicle  22   a - d  has entered the departure transition zone  20 . Structurally, the toll collection device  28   a - e  and the sensor  30   a - e  are positioned on the approach side of the start point  16   a - e,  while the indicator  26   a - e  is positioned between the departure transition zone  20  and the toll collection device  28   a - e.  Further, a plurality of transmission lines  32  runs to and from the computer  24  and allows for the sending and receiving of electronic signals to and from the indicators  26   a - e,  toll collection devices  28   a - e,  and sensors  30   a - e.    
         [0014]      FIG. 2  further indicates that the present invention is controlled by the computer  24 . After the vehicle  22   a - d  pays the required toll, the toll collection device  28   a - e  registers the payment with the computer  24 . When the toll is registered, the sensors  30   a - e  electronically send an arrival signal to the computer  24  to indicate the presence of the vehicle  22   a - d  at the start point  16   a - e.  Then, the computer  24  processes the information received using a pre-programmed departure schedule and queues the vehicles  22   a - d  for entry into the travel lane  18 . After determining the vehicle  22   a - d  can depart the start point  16   a - e,  the computer  24  sends an electronic departure signal to the corresponding indicator  26   a - e  to allow the vehicle  22   a - d  to move from the start point  16   a - e  into the travel lane  18 . At the same time, the computer  24  sends signals to the indicators  26   a - e  for all other vehicles  22   a - d  at start points  16   a - e  to remain in place. 
         [0015]    When assigning each vehicle  22   a - d  a relative start time, the computer  24  considers four pre-programmed time delay variables. Specifically, the four time delay variables are defined as follows: Δ 1  is the time delay established between starts for sequential vehicles in Zone A; Δ 2  is the time delay established between starts when a vehicle in Zone A follows a vehicle in Zone B; fΔ 1  is the time delay established when a vehicle in Zone B follows a vehicle from Zone A; and hΔ 2  is the time delay established between starts for sequential vehicles in Zone B. The resultant, or staggered, start times ensure vehicles  22   a - d  leaving the start points  16   a - g  will have adequate spacing and not cause a traffic delay in the departure transition zone  20 . As illustrated, Zone B is located further from the travel lane  18  than Zone A. Establishing values for these variables will account for the individual characteristics of each toll plaza  12 . Moreover, values for the variables can be updated at any time to more accurately reflect traffic conditions at the toll plaza  12  or any physical changes made to the toll plaza  12  or the travel lane  18 . 
         [0016]    As envisioned for the present invention, Δ 2 &gt;Δ 1 , f&lt;1, and hΔ 2 ≈Δ 1 . This allows more time for the vehicle  22   c  entering from Zone B to get ahead of the vehicle  22   a  entering from Zone A. This is necessary since the Zone B vehicle  22   c  must traverse a greater distance through the departure transition zone  20 . For the vehicle  22   c  in Zone B, the shortened delay, fΔ 1 , accounts for the head start advantage of the Zone A vehicle  22   a  which has a shorter distance to travel from the start point  16   a  to the travel lane  18 . Consequently, f&lt;1, and is envisioned to be in a range of about 0.5 to 0.8. Finally, hΔ 2  provides the time delay for sequential vehicles  22   c - d  coming from Zone B. Since both Δ 1  and hΔ 2  both relate to sequential vehicles leaving the same zone, their values will likely be the same. 
         [0017]    Referring to  FIG. 3 , a logic chart shows the operation of the pre-programmed departure schedule at each start point  16 . As shown, the first inquiry is whether the vehicle is next (see inquiry block  34 ). If the vehicle is not next, it waits at action block  36   a.  If the vehicle is next, the computer determines if the vehicle is in Zone A. If the vehicle is in Zone A (see inquiry block  37 ), it proceeds to inquiry block  38 . If Δ 1  is equal to zero at inquiry block  38 , the vehicle proceeds to inquiry block  40 . If Δ 1  is not equal to zero, the vehicle waits at action block  36   b.  At inquiry block  40 , if Δ 2  is zero, the vehicle is released into the departure transition zone at action block  42  and the two Δ 1  variables are reset. If Δ 2  is not equal to zero, the vehicle will wait again at action block  36   b.    
         [0018]    Still referring to  FIG. 3 , if the vehicle is not in Zone A (see inquiry block  37 ), the status for vehicle  22   c - d  proceeds to block  44  to determine whether fΔ 1  is equal to zero. If it is, the status for vehicle proceeds to inquiry block  46 . If fΔ 1  is not equal to zero, the vehicle  22   c - d  waits at block  36   c.  If fΔ 1  is equal to zero, the vehicle proceeds to block  46  where the value of hΔ 2  is determined. If hΔ 2  is equal to zero, the vehicle  22   c - d  moves to action block  48  where it enters the departure transition zone  20 . If hΔ 2  is not equal to zero, the vehicle waits at action block  36   c.    
         [0019]    Operationally, four scenarios are possible using the logic chart. For the purposes of the four scenarios, consider vehicles  22   a  and  22   b  are at start points located in Zone A and vehicles  22   c  and  22   d  are located at start points in Zone B (see  FIG. 1 ). The four scenarios are as follows: a vehicle  22   b  from Zone A following another vehicle  22   a  from Zone A; a vehicle  22   c  from Zone B following a vehicle  22   a  from Zone A; a vehicle  22   a  from Zone A following a vehicle  22   c  from Zone B; and a vehicle  22   d  from Zone B following another vehicle  22   c  from Zone B. 
         [0020]    In the first scenario, a Zone A vehicle  22   b  follows another Zone A vehicle  22   a.  Using the logic chart, vehicle  22   b  is at the start point as soon as vehicle  22   a  is released at action block  42  and the value for Δ 1  is reset. As vehicle  22   b  reaches the start point and is determined to be next in the queue and in Zone A, the status of vehicle  22   b  moves to block  38  and waits at block  36   b  until Δ 1  is equal to zero. Once Δ 1  is zero, the status moves to inquiry block  40 , and moves forward because Δ 2  must be equal to zero for vehicle  22   a  to move into the departure transition zone  20 . When the previous vehicle did not depart from Zone B, the values of Δ 2  and hΔ 2  are zero. 
         [0021]    In the second scenario, a Zone B vehicle  22   c  follows a Zone A vehicle  22   a.  As vehicle  22   a  enters the departure transition zone  20  at block  42 , the value for Δ 1  is reset. Once the value for Δ 1  is reset and vehicle  22   c  is determined to be next and not in Zone A, vehicle  22   c  moves to inquiry block  44  and waits at block  36   c  until the value for fΔ 1  is zero. When the value for fΔ 1  is zero, vehicle  22   c  moves through inquiry block  46  to action block  48  and enters the departure transition zone  20 . Because the previous vehicle  22   a  left from Zone A, the value for hΔ 2  remained at zero allowing vehicle  22   c  to move through inquiry block  46 . 
         [0022]    In the third scenario, a Zone A vehicle  22   a  follows a Zone B vehicle  22   c.  Once vehicle  22   c  enters the departure transition zone at block  48 , the value for Δ 2  is reset. After vehicle  22   c  enters the departure transition zone, vehicle  22   a  is determined to be next and to be in Zone A. Vehicle  22   a  moves through inquiry block  38  because Δ 1  is equal to zero since the previous vehicle exited from Zone B, so the value for Δ 1  remained at zero. Next, vehicle  22   a  reaches block  40  and waits at action block  36   b  until A 2  is equal to zero before moving to block  42  and into the departure transition zone  20 . 
         [0023]    In the fourth scenario, a Zone B vehicle  22   d  follows another Zone B vehicle  22   c.  As vehicle  22   c  enters the departure transition zone  20 , vehicle  22   d  moves from the start point  16   e.  Once the pre-programmed departure schedule determines vehicle  22   c  is next, it moves to inquiry block  44  because vehicle  22   d  is not in Zone A. At block  44  fΔ 1  is equal to zero and Δ 1  is equal to zero since the previous vehicle left from Zone B meaning Δ 1  was not reset. Next, vehicle  22   d  moves to inquiry block  46  and waits at block  36   c  until the value of hΔ 2  is zero. Once hΔ 2  is zero, vehicle  22   d  moves to block  48  and into the departure transition zone  20 . 
         [0024]    While the particular System for Metering Vehicular Traffic at a Toll Plaza as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.