APPENDIX 7 - LEVEL OF SERVICE (LOS)

In Section IV.I. of the Zoning By-Law (Site Plan Review) the standard set forth for traffic impacts is based on the concept of "level of service" ("LOS"). Level of service is a qualitative measure of the operating condition of a transportation facility, such as an intersection or highway link, at specific traffic volumes. It is divided into six classes described as follows:

 LOS                            Operating Conditions                           

  A    Free flow, low volume, high operating speed, high maneuverability.      

  B    Stable flow, moderate volume; speed somewhat restricted by traffic      
       conditions, high maneuverability.                                       

  C    Stable flow, high volume; speed and maneuverability determined by       
       traffic conditions.                                                     

  D    Unstable flow, high volumes, tolerable but fluctuating operating speed  
       and maneuverability.                                                    

  E    Unstable flow, high volumes approaching roadway capacity, limited       
       speed,                                                                  
       intermittent vehicle queuing.                                           

  F    Forced flow, volumes lower than capacity due to very low speeds.        
       Heavy queuing of vehicles, frequent stoppages.                          

[Source: "Quick-Response Urban Travel Estimation Techniques and Transferable Parameters: User's Guide", National Cooperative Highway Research Program Report 187, Transportation Research Board, National Research Council, 1978]

LOS is determined differently for highways, signalized intersections, and unsignalized intersections. Capacity and level of service of signalized intersections are determined using a procedure known as Critical Movement Analysis. In this method, LOS is determined by vehicle delay and "volume/capacity (V/C) ratio", which is the sum of "critical volumes" for the intersection divided by the theoretical capacity of the intersection. The following table summarizes the delay and V/C values for signalized intersections:

                                              Delay Range         
 Level of Service  Typical V/C Ratio         (sec/vehicle)        

        A               .00-0.60               0.0-16.0           

        B               .61-0.70               6.1-22.0           

        C               .71-0.80               22.1-28.0          

        D              0.81-0.90               28.1-35.0          

        E              0.91-1.00               35.1-40.0          

        F                varies             40.1 or greater       

[Source: "Interim Materials on Highway Capacity", Transportation Research Circular No. 212, Transportation Research Board, National Academy of Sciences, January 1980, pp. 5 - 12.]