01 - Basic of traffic flow and management - SM

Traffic engineering story

1886: Benz's patent for motorcar

Traffic flow variables

Spacing

spacing ($s$)

Spacing is the distance between the front of 2 cars.

Headway

Headway ( $h$ )
Headway is the time between two vehicles (front to front).

Speed

Flow

Flow ( $Q$ ) is the number of vehicles observed at a certain point in unit of time.

It's measured in $[\frac{v e h}{h}]$

Density

Density is the number of vehicle observed at a certain time per unit of length.

Time mean Speed

time mean speed ($tms$ or $v_{t}$)

The Time mean Speed is the average velocity based on time.

$v_{t} = \frac{\sum_{i = 1}^{N} v_{i}}{N}$

Determine each car speed in one point
Average them out

Space mean speed

space mean speed ($sms$ or $v_{s}$)

The Space mean speed is the average velocity based on distance travelled

v_{s} = \frac{L}{\sum_{i = 1}^{N} \frac{t_{i}}{N}} = \frac{N}{\sum_{i = 1}^{N} \frac{1}{v_{i}}} = \frac{\sum_{i = 1}^{N} v_{i}}{N}

Select a road section of knonw length
Measure the time it takes each veh to go through the section
Calculate using the formula

Time space diagram

See:

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I stopped paying attention for a while, since we already did all of this in 🚦 OMT.

Fundamental relationship of traffic

01 - Introduction to trajectories Analysis - OMT#Fundamental equation of traffic

$k :$ density
$q :$ flow

k = \frac{N}{T} = \frac{1}{s} q = \frac{N}{T} = \frac{1}{h}

u = \frac{s p a c e}{t i m e} = \frac{s}{h} = \frac{\frac{1}{k}}{\frac{1}{q}} = \frac{q}{k}

therefore:

q = k u

Traffic flow diagrams

Importance of traffic variables in sustainability

They directly influence pollution levels by affecting fuel consumption and emissions.

When traffic is heavy, cars move slowly or stop often, increasing emissions per trip.

Emission factor

They are values that show how much pollklution a specific source releases into the air, for example grams of CO2 per kilometre.

Traffic dynamics

Traffic distribution in networks

Traffic control and management

Software for traffic simulation

See video:

and:

We can model several strategies:

TC and MS (traffic control and management strategies) are methods used to regulate and optimise the flow of vehicles to reduce congestion.

Dynamic management of speed limits
Dynamic lane assignment
- Reversible lanes
- Dynamic use of hard shoulder
- High occupancy veh lanes
Incident management
Autonomous driving
Freeway access management
- Ramp metering