Midterm Revision Flashcards
What are the possible impacts of transport infrastructure investments?
Reducing Travel Costs (Operating costs & Travel Time)
Thus;
- Creating employment
- Reorganization or rationalization of production and distribution
- Unlocking inaccessible sites for development
- Increases in output resulting from lower costs of production
What is traffic?
Change of locality of persons, goods and information
What are Transport Networks?
Due to the need to perform changes of locality, networks of paths and roads evolved.
What is Accessibility?
Accessibility refers to the new ease of reaching goods, services, activities and destinations, which are called opportunities. It can be defined as the potential for interaction and exchange
What is mobility?
Mobility is about getting from location A to location B.
Categories of Road structures?
Cat 1: Expressway, long distance traffic movements should be directed.
Cat 2: Major Arterial, carries through from one region to another, It interconnects expressways and minor arterial as well as with other major arterial.
Cat 3: Minor Arterial, distributes traffic within the major residential and industrial areas.
Cat 4: Primary Access, forms the link between local accesses and arterial roads. It provides access to developments and through traffic is discouraged
Cat 5: Local Access, gives direct access to buildings and other developments and should connect only with primary access
Management of traffic demand
Avoid that the new space will be re-occupied by new cars withing short time
Push: restrictions for private traffic
Pull: Improvements in public transport
3 level of measures in Management of Traffic demand
- Avoid Traffic (Demand)
- causes of traffic - Shift Traffic (Demand)
- time/space/mode - Operate Traffic
- regulate (like ERP)
Some example of Transport Demand Management measures
- Land use development controls
- Regulatory controls such as odd/even systems
- Pricing & charges through fuels, annual taxes
- Congestion charging
- Parking controls and management
- Public transport integration
- Physical measures such as bus and pedestrian priority
TDM policies should never be implemented as isolated instruments, but - for being successful- have always to be embedded in a comprehensive framework of Transport Demand Management measures.
What are some measures with push effects?
Area-wide parking management
Parking space restrictions in zoning ordinances, car limited zones, permanent or time of day car bans, congestion management, speed reductions, road pricing
Why do we need traffic models?
- The reality is complex
- Models are simpler
Models can help us understand and investigate interesting phenomena of real world of mobility and transportation systems
Steps in Modelling
- Problem Definition
- Objects, interdependencies and processes on objects - Model World
- Data Structure, Algorithms - Computer simulation
- Data objects and Procedures
Requirements to models
- Sensitivity
. ability to model interesting effects in a sensitive and reliable way as close to a specific area with a specific mode of transport activity as possible or necessary - Logical Consistency
. The structure must be consistent, eg. it should not allow for internal contradictions - Operability:
. The implementation and application must be possible within reasonable effort. - Transparency:
. The structure must be clear and understandable, so that results can be understood and double-checked. - Reliability:
. Same results if experiment is repeated with the same external conditions - Validity
. Results must be valid
Different Types of Models:
Demand Models:
Forecast the number of trips between origins and destinations specific area with a specific mode of transport
Activity based models:
predict for individuals where and when specific activities are conducted and construct a demand pattern
Data driven models:
purely statistical models that make use of patterns in traffic data to make predictions
Traffic flow models:
predict traffic density and traffic volume
Levels of details in Traffic Simulation Models:
Macroscopic levels:
aggregate traffic flow characteristics of a traffic stream, like density, flow, mean speed, etc., predioctions of speeds are an average of the traffic flow on a specific road specific section in a network
Mesoscopic levels:
is a range of models that use groups of vehicles as starting point for the traffic flow condition calculations (combines properties of both microscopic and macroscopic simulation models)
Microscopic levels:
Vehicles simulated individually, as realistic as possible, eg. time headway, distance between two cars, location of a single car. Time consuming, costly, and can be difficult to calibrate.
Sub-microscopic level:
Detailed vehicle models (veh components) are studied individually
Static: the impact of spill back due to congestion is neglected.
Dynamic: spill back due to congestion is considered.
Basic Transport Planning Model
- Which activity?
- Which mode?
- Which destination?
- Which route?
The basic transport planning model in 4 steps:
- model: Traffic generation (Demand) (traffic at Origins and Destinations)
- model: Traffic Distribution (Origin to Destination)(Destination Choice)
- model: Split to Transport Means / Modal split (Mode Choice)
- model: Routing and Assignment of Demand to a network (Route Choice)
The 4 steps planning rocket delivers the amount of traffic that moves through a network
- The planning rocket delivers the amount of traffic that moves through a network
This is one starting point for the use of traffic flow models.
Traffic flow models provide ways to describe the traffic movements in more detail and thus can deliver detailed results of the effects of some transport planning approaches
Another starting point for the use of traffic flow models is online mgmt and control. The models are used to determine the current and predicted dynamic traffic situation.
Traffic flow models are also used for the detialed anlaysis of field traffic data, for data completion in case of faulty or missing data, for prognosis studies, effect analyses, simulation, etc
Traffic flow models use different resolutions depending on their purpose
Why do we need microscopic flow model?
- Vehicles do not drive with constant velocity
- Vehicles have different capabilities
- Drivers don’t behave equally
- Want to know vehicle-specific info
Which aspects of microscopic view are important for modelling?
- Car-following behaviour
- Lane changing on road sections
- Merging behaviour at on-ramps and intersections
- Reaction to / interaction with infra and control devices
- Interaction of driver and vehicle components.
Car Following Models
- Psycho-physical car-following models are used in microscopic simulation tools
- Used in Advanced Driver Assistance Systems for Adaptive Cruise Control or collision avoidance systems
- Semi-automated driving
- using VISSIM
There are 2 types of Car-following Models
- based on kinematics
- kinematics and drivers behaviour
First Car Following Model (Diff. in velocity, reaction time and intensity, distance and safety distance)
Sensitivity is constant and not depending on distance and speed = linear car following model
Sensitivity is dependent on distance and speed = non-linear car following model (Gazis, Herman and Rothery Model)
Second Car Following Model (Which includes Driver’s behavior)
If Desired Velocity and restrictions are considered: Gipps Model
If Considering Driver behavior, perceptional thresholds, ‘tactical driving’: Psycho-physical car-following model & Intelligent Driver Model.
