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Verkehr I

Norman Garrick

Norman Garrick

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Cartes-fiches 57
Langue English
Catégorie Code de la route
Niveau Université
Crée / Actualisé 03.08.2021 / 14.08.2021
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Definition: Access, Accessibility

Ability/opportunities to reach the desired destination

is defined through:

  • Generalised cost: Travel Time, Cost, Comfort
  • Proximity of bus station

Goal of Transportation Planning: maximize Accessibility

=> for higher productivity & more user for public transport

 

Definition: Impendance function

describes difficulty to reach a destination 

Definition:

- User Equilibrium 

- System Equilibrium

System Equilibrium

  • minimal total generalised cost
    => additional car makes other cars slower

User Equilibrium:

  • shortest route for all users
    => used routes have same generalised cost
    => not used ones have higher cost
  • illustrated through Minimum Tree

Time Mean Speed

Space Mean Speed

TMS

  • measured with radar scanner
  • = arithmethic average of spot speed:\(u_t =\frac{\sum v_i}{n}\)

SMS

  • areal photograph
  • total distance/total time
  • harmonic mean: \(u_s =\frac{n}{\sum{1/v_i}} \)

Draw the traffic flow curves

- u-k

- u-q

- k-q

-> siehe Notion

Definition: directional distribution

- factors, affects on design

- Solution

Difference of traffic flow in two opposite direction

  • Travel flow during peak hours is mainly focused in one direction
    => generated through insufficient land use mix
  • problem: empty streets & pt in other direction => insufficient use of infrastructure

Solution

  • mixed land use
  • reversible lande
  • zipper machine

Solution to reduce temporal variation of traffic flow

  • mixed land use
  • differential pricing: higher charge of transport systems during rush hour
    => ppl who are not dependent on traffic during peak hours delay their travel

Characteristics of Travel Flow

  • temporal variations: traffic flow depends on observation time & space, peak hours, 
  • spatial variation:
    • Travel flow depends on local land use (city: higher q)
    • depends on the infrastructure provided (street width)
  • depending on travel direction
  • change of transportation & land use changes travel flow as well

How is traffic data being collected?

- permanent & temporary count stations

- GPS data

 

Definiton: ADT

How is ADT being collected

Why is ADT alone not sufficient for traffic planning

?

Charactersistics of Capacity

Capacity of a street is not fixed but based on level on level of congestion we are willing to put up with
=> determined by a desirable Level of Service
-> based on Social, Economic, and Tracel Capacity
=> is a political number

- characterized by DHSV: Design hourly service Volume

Definition: Design Hour Volume DHV

- issues of DHV

- how to select DHV

for traffic planning we need to set a future time we want to plan/design for

  • DHV describes traffic occurence in the design hour & year and in the design direction for the design capacity (based on Level of Service)
  • estimated from ADT

How to select DHV:

  • traffic planning for the traffic occurence of 50th-200th most busy hour of the year

Problems:

  • Determining DHV is a Trade off between too many congestion hours & inefficiently big facility
  • When Design year >20 y in the future: predict & provide

Definition "predict and provide" Approach

- problematics

  • Traffic design solely based on past trends & numerial datas
  • doesn't take into account societal parameters, like change of mindset, that can influence traffic occurence

Problems

  • reacting instead of acting
  • Induced Traffic: 
    • wider streets -> attracts more cars -> bigger traffic occurence than predicted -> again wider streets
  • unpredictable occurence -> more traffic in comming year -> again predict & provide -> massive & insufficiently used infrastructure
  • wrong assumptions
  • new technologies

Definition: Level of Service

- Problematics of low LOS

= What level of traffic concentration do we want to have for design hour?

low LOS:

disigning a low LOS during busiest hour of the year => broad streets

=> Empty & insufficiently used street for the rest of the time

 

Calculation: Number of Lanes

Nr. of Lanes = DHV/DHSV

- DHSV: given by LOS

- DHV = ADT * Directional Split * Traffic in Designhour (as fraction of ADT)

5 Levels of Autonomous Driving

  1. driver assistance
  2. partial automation
  3. conditional automation
  4. high automation
  5. full automation

Evolution of the Urban Form (through Transportation)

  • before cars: compact cities that were designed for walking
  • cars & electric rail changed shape & size of city
  • faster travel BUT not reduction in total travel time (-> 30-minute commute principle)

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