Road Transport Systems

• Urban traffic lights
• Ramp metering
• Variable speed limits (VSL)
• Variable message signs (VMS)
• Route guidance

• Car pooling
• Congestion pricing
• Mode choice

Links:

• main road
• freeway
• link road
• local street
• etc...

Nodes:

• Stop sign
• Overpass
• Ramp
• Level crossing
• Traffic light
• stop sign
• roundabout

• Telematics
  - IT: Information Technologies
  - Communications
  - Hardware/Software
• Long distance transmission of data and computerized information
• Sensor, road network instrumentation, wireless communications
• Algorithms for traffic estimation, prediction and traffic management

measurements...

• ...at a (cross-sectional) point
• ...along a short distance
• ...along a length
• ...along an arterial or small area (by e.g. moving observer method)

other real-time large-scale monitoring methods

• the process of combining data from multiple, heterogeneous data sources such as cross-sectional data, floating-car data, police reports, etc.
   
• each of these categories of data describes different aspects of the traffic situation and might even contradict each other
   
• the goal of data fusion is to maximize the utility of the available information

• Autonomous/connected vehicles and planning models
   
• Implications to traffic flow and operations
   
• Simulation: traffic, wireless communications
   
• Trajectory processor for particle-based simulators
   
• Lane changing in connected environment: game theory

Vehicle classification:

Different types show distinct signature data

Basic independent control unit.

• At least
  • 1 Detecting element
  • 1 Display element
• Possible traffic streams
  • Automobile traffic
  • Bus transit
  • Light rail transit
  • Pedestrians
  • Bicyclists
  • Emergency vehicles

Driving a vehicle in the traffic stream, trying to maintain an "average" position in the traffic stream, i.e:

passing only as many vehicles as pass you.

• The most widely used sensors (for TM)
  • magnetic field
  • easy to install, inexpensive
     
• Measurements:
  • time occupancy (%)
  • flow (number of vehicles)
  • speed (for double loops)

• Detectors that
  • call for green (presence)
  • ask for green extension (queue)
     
• Utilized in many cities with advanced management systems

Traffic lights exist to control the flow of traffic and are expected to bring benefits:

• Increased safety
• Minimize accident frequency and severity
• If properly timed, a traffic signal increases the traffic handling capacity of an intersection
• Manage traffic and travel times
• Provide directions to drivers

Phase: The sum of the displayed green, yellow and red times for a movement or combination of movements that receive the right of way simultaneously during the cycle.

Stage: A group of phases that receive the right of way simultaneously during the cycle for an intersection.

Cycle: The sum of the phase lengths is the cycle length.

Protected movement: A movement that has the right of way and does not need  to yield to conflicting movements, such as opposing vehicle traffic. Through movements, which are always protected are given a green indication.

Permitted movement: A movement that must yield to opposing traffic flow. This movement is made during gaps.

Can be determined by using the cross-product.

Cross product rule helps us identify if a movement should be protected or permitted. The cross-product is a simple approach that is only dependent on the peak-hour traffic flows \(\nu\).

Generally, we take the peak-hour traffic flow value of the traffic movement we want to check on protected movement and the opposing traffic movements. The determined values are checked against thresholds.

• Cross product exceeds 50'000 vehicles during peak-hour for one opposing lane
• Cross product exceeds 90'000 vehicles during peak-hour for two opposing lanes
• Cross product exceeds 110'000 vehicles during peak-hour for three or more opposing lanes

Cross Product:    \(CP_{\phi_i,\phi_j} = v_i \cdot v_j\)

A stage is a group of phases (i.e. movements) that don't create conflicts and are compatible, i.e. they can operate together.

Undersaturated conditions: all the vehicles that are queued during the red phase are served by the green.

Saturated conditions: vehicles spend in the intersection more than one cycle (cycle failure).

Pre-timed: A signal whose timing (cycle length, green, red etc.) is fixed over specified time periods. This is not affected by traffic flow at an intersection.

Semi-actuated: A signal whose timing is affected when vehicles are detected (by video, loop-detectors or other sensors), on some, but not all approaches. This approach is met on major/minor roads (with difference on flows). The major gets green until some vehicles appear in the minor.

Fully-actuated: A signal whose timing is completely inflluenced by traffic flow. This approach is met on major/major roads where substantial variations exist in the approaching traffic volumes.

Aggregated relationship between network accumulation and total flow (production).

Useful tool for control.

1. undersaturated: minimize delays!
    
2. saturated: maximize capacity!
    
3. oversaturated: queue management, gating!
    
4. blocked: call the police or walk home!

The saturation flow is the hourly maximum volume that can pass through an intersection, from a given lane (or group of lanes), if that lane was allocated constant green over the course of an hour.

\(s= \frac{3600}{h} [\frac{vehicles}{h}]\)

s is the saturation flow in vehicles per hour
h is the saturation headway in seconds per vehicle
3600 is the number of seconds per hour

Movements on an intersection do not receive a constant green indication. Capacity accounts for the hourly volume that can be accommodated on an intersection.

\(c=s \frac{g}{c} [\frac{vehicles}{hour}] \\s \ \text{ is the saturation flow in vehicles per hour.} \\g \ \text{is the green time in seconds} \\C \ \text{is the cycle length in seconds}\)

Due to the traffic signal's function of continuously alternating the right-of-way between conflicting movements, traffic streams are continuously started and stopped. Every time this happens, a portion of the cycle length is not completely utilized, which translates to lost time.

\(t_L = t_{sl} + t_{cl} \\ \\t_L \ \text{is the lost time for a movement during a cycle in seconds} \\t_{sl} \ \text{is the start-up lost time in seconds} \\t_{cl} \ \text{is the clearence lost time in seconds}\)

Occur because when a signal indication turns from red to green, drivers in the queue do not instantly start moving at the saturation flow rate. The stopping of a movement also results in lost time. The yellow-red transition or all-red times are not fully utilized as well. This refers as clearance lost time.

The amount of time within a cycle in which all approaches have red indication. This time is referred to as clearance intervall.

Macro-level

Meso-level

Micro-level

TAZ divide the study area into smaller regions assumed to be homogeneous demographically and economically.

Zone selection criteria:

• Homogeneous socioeconomic characteristics
• Minimize the number of intra zonal trips
• Recognize physical, political and historical boundaries

Zone Centroid: Special node whose number identifies a zone, located by (x, y) coordinates.

Node (Vertices): Intersection of links, located by (x, y) coordinates.

Links (Arcs): Indexed by from and to nodes (including centroid connectors), attributes include lanes, capacity per lane, allowable modes.

Turns: Indexed by at, from and to nodes.

Routes (paths): Indexed by a series of nodes from origin to destination (e.g. a public bus line)

Modes: Car, bus, HOV, truck, bike, walk etc.

Surveys (traditional method)

ICT and Big-data movement (cities are data-factories!)

Internet (FB, Twitter, Foursquare, Instagram, etc.)

Cellular phones (Bluetooth)

https://opentransportdata.swiss/

1. Trip generation: What are the total number of trips people make to and from each zone?
    
2. Trip distribution: What are the specific origins and destinations for this total number of trips?
    
3. Mode choice: How many people will choose to drive, walk, cycle, use transit, etc.?
    
4. Route choice: What are the specific routes that people will use for their trips?

Origin-Destination Matrix or Trip Table

For modelling Mode choice some consistent theory of decision-making is needed:
--> Microeconomic concept of utility maximization is most widely accepted

Basic assumption:

• Traveler will select the combination of the mode that gives the most utility economically
• this is modelled with a so called utility function

The utility function for Mode choice can include:

• location (proximity to bus stop)
• convenience
• cost
• travel time
• parking
• health
• environment
• privacy (i like to travel alone)
• ...