# Level of Service and Factors Affecting LOS

## Definition:

LOS is a scale which defines the operating conditions on highway. It is a measure of the restrictive effects of the increased volume, level of service as proposed by manual ranges from A to F, A is ideal level and F is worst level of service.

LOS |
Max.Density (PC/min/lane) |

A | 12 |

B | 20 |

C | 30 |

D | 42 |

E | 67 |

F | > 67 |

### LOS A:

Density is low enough that closeness of vehicle do not effect vehicle movement

### LOS E:

No usable gap between vehicles, speed is slow,, condition can easily cross over into LOS F region.

### LOS F:

Breakdown condition, number of vehicles arriving > number of vehicles leaving, speed is zero.

## Elements to evaluate LOS:

- Travel speed and travel time
- Volume to capacity ration (V/C) ratio
- Density (number of vehicles per unit length on highway, D=F/S, where S is speed and F is flow in pcph)
- Delay (at intersection, signals) If V/C =1 (level E) V/C >1 level of service is low
- Peak hour factor (PHF): The ratio between flow for entire peak hr and the maximum hourly rate of the flow during 15 minute of that hour
- Service flow = SF = V / PHF = Peak hour volume / PHF

Where = Correction factor for road width

= Correction factor for heavy vehicle

= Correction factor for driver population

F HV = 1 / ( ( 1 + Pt ( Et - 1 ) + Pb ( Eb - 1 ) + PR ( ER - 1) )

Et, Eb, ER,, Passenger car equivalent for truck, bus and recreational vehicles.

Pt, Pb, PR,, Proportion of respective class vehicles N is the number of lanes in one direction. CJ is the capacity per lane (pcphpl)

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