Vehicle Delay Study

Before anything else Read the manual carefully. It is

your homework What is covered in the following

slides is just general

General Determines LOS of lane

group/approach Measured by seconds delayed for

eachvehicle! Simplification of Highway Capacity

Manual HCM

Collect the data Choose intersection

Signalized intersections Choose time of day

Usually peak hour Choose the approach

You may need to zoom in further to a specific lane group

Exclusive left turn is studied by itself

Collect the data For illustrations let us study delay

of an exclusive left turn lane

Collect the data First observer counts and records

the number of vehicles stopped on the left lane for each 15 seconds interval

A vehicle is counted more than once in the delay determination if it is stopped during more than one sampling time.

Collect the data The second observer performs a

separate tabulation of the lane volume for one minute intervals by classifying the vehicles as either stopped or not stopping.

At least 350 cars must be counted

Numbers in that column can’t be true!

Data Analysis Two calculations are needed

General calculations For sake of LOS determination

Data Analysis General

calculations

ondssec9.9233

2310233

15541eper vehicl delayed seconds

delayed vehiclesof volumeTotal15intervalsdelay in vehiclesofNumber eper vehicl delayed seconds

Data Analysis General

calculations

%57409233delayed volume totalof %

100counted vehiclesof volumeTotal

delayed vehiclesof volumeTotaldelayed volume totalof %

Data Analysis For sake of LOS determination

Correction factors: acceleration deceleration Vehicles processed in less that 15 sec

All of that is accounted and used in the simplified way:

Data Analysis For sake of LOS determination

ondssec3.73.140923103.1

40915541eper vehicl delayed seconds

3.1counted vehiclesof volumeTotal

15intervalsdelay in vehiclesofNumber eper vehicl delayed seconds

LOS Compare that number to the

following table

Calculations repeat this analysis for the other

approaches of the intersection Prepare a graphical representation

for the delay and LOS of each lane group

Interpret and conclude Answer questions in manual Prepare your presentation