Transportation def
the application of scientific principles to the
planning, design, operation and management of
transportation systems
• Goal: safe, efficient, convenient and economical movement of people and goods
Transport modes and systems
1) Road (car, bus, truck) 4) Air
2) Rail 5) Pipeline 3) Water (inland, ocean) 6) Intermodal • System components – fixed
– Transport lines or “ways”: highways, waterways– Terminals: ports, airports, railway stations• System components – mobile
– Units of carriage: wagons, trailers, barges
– Units of propulsion: locomotives, tractors, tugs
– Self-propelled units of carriage: trucks, ships
Transport system characteristics
• Variables used to characterize a transport system:– Speed– Frequency– Unit capacity (one vehicle, vessel)– System capacity or throughput per unit time
• Transport system performance criteria:
– Travel/transit time– Reliability
– Price (cost) per passenger-km, tonne-km
– Safety (accident rate)
– Security (risk of loss or theft)
Issues and challenges
• Traffic congestion - building more roads does
not reduce congestion
• Safety of transport - concern most visible in road and air modes
• Environmental protection – reducing both sitespecific and system-wide impacts
• Application and taking advantage of the new
Technology
Transport policy options
• Alternative policy strategies:
– pro-car strategy (building more roads & car parks)– car-free city (severe restrictions on car use)– sustainable development (balanced approach:
restraint on cars in certain zones + public transport(PT) improvements)
• Sustainable development = economic growth while
maintaining the stock of natural resources
Transport policy aims & measures
• Policy aims are realised through:
– reduction of travel demand – control of sprawl
– reducing dependence on cars
– promoting alternative modes: PT, cycling, walking
– developing effective and environmentally friendly PT
• Transport policy measures
– creation of restricted access zones (traffic cells)
– parking fees and road pricing
– integration of different modes of transport
– traffic calming in residential areas
– public transport improvement measures
Transport policy - 3 zones
• Zones with different roles of private cars and PT
• Zone A (city centre)
– major role of PT – priority of PT in traffic
– restraint on car use: limited access, parking fees
– pedestrian streets
• Zone B (intermediate)
– PT developed in corridors of travel concentration
– some parking restrictions
• Zone C (peripheral)
– equal treatment of PT and car traffic
– traffic calming in residential areas
Systems approach to planning
Emphasis on goals, planning as a continuous process:
1. collection of demographic and travel data
2. analysis of data
3. formulation of goals and specific objectives
4. development of alternative plans for achieving
objectives
5. evaluation of the alternative plans
6. implementation of the selected plan
7. monitoring and review of its effectiveness
Travel Surveys
• Aim: to establish an understanding of travel patterns
within study area
• Involve interviewing a sample of travellers to obtain
information on their travel behaviour
• Origin-Destination (O-D) survey:
– 1. Establish zones
– 2. Conduct survey
– 3. Do screenline check
– 4. Analyse/expand data Urban travel forecasting• Planning of urban transportation systems requires knowledge the future travel pattern• Future travel demand may be different because:– land use locations may change – cities develop– demography may change – population, family size– economic conditions may change: car ownership,employment, income• Models are developed based on survey findings about the present and applied to future conditions4-step transport modelling process• Trip generation – establishing the relationship between trip making and land-use factors in a zone• Trip distribution – determining the pattern of trips between zones - establishing an O-D trip table• Modal split – division of person-trips among the different modes of travel, based on relative costs• Traffic assignment – allocation of traffic flows to alternative routes between origin and destinationRoad classification – 4 classes:• Expressways –– provide fast/high volume movement to major activity centres– access is controlled using grade separation (multi-level intersections)• Arterials– intermediate movement function from expressways to collectors– distribute traffic to district centres and industry• Collectors – mixed movement and access function– distribute traffic between arterials and local roads• Local streets – predominant access function– provide access to individual buildings
Environmental area concept
• A space where people can move around on foot, in reasonable freedom from hazards of motor traffic– The design should ensure that traffic is compatible
with the conditions sought
– Cell urban structure – environmental areas are set within a network of highways
– Road network is to serve the environmental areas –major traffic flows are channelled around the cells
• Application: planning of residential areas and town centres in many countries
Human physiological characteristics
• Vision – seeing range: ellipsis of clear vision
– ability to adapt to bright light and darkness
– sensitivity to glare
– seeing in 3 dimensions (distance estimation)
– colour recognition (traffic signals)
• Hearing – most important for pedestrians
• Concentration – significant factors:
– divisibility
– capacity (stimuli/min)
– sustainability (focusing)
– mobility (switching)
Conclusions for road design
• Uniformity of road design - drivers do not expect changes
• Clear demarcation of the driving path
• Limiting the number of simultaneous choices
• No unnecessary distractions for drivers
• Variation of scenery (monotony is dangerous)
• Consideration of eye adjustment ability to lighting conditions
• Design of road signs and traffic signals –
positioning, effect of speed
• Provision of resting opportunities for long trips
Traffic flow parameters
• Traffic flow (q) is the number of vehicles passing a road section per hour (or sec)
– expressed in veh/h or veh/s
• Density (k) - number of vehicles per km - is the
inverse of the average spacing
• Speed (v) – average speed of traffic (km/h)
• Fundamental traffic relationship:
q = k v [P/h] = [P/km]*[km/h]
Highway Capacity Manual
• Need for capacity analysis:
– To assess existing operational conditions
– To design new facilities determine no. of lanes – To provide values for economic analysis
• HCM has evaluation procedures for:
– Uninterrupted flow facilities: freeways, expressways,
2-lane 2-way roads
– Interrupted flow facilities: signalised and unsignalised intersections
– Other facilities: public transport, pedestrians and Bicycles Capacity – definitions • Capacity of a facility - maximum hourly rate at which vehicles can pass a section of a road, under prevailing road, traffic and control conditions • Level of Service (LoS)– a qualitative measure that characterises operational conditions and their perception by motorists
• Ideal conditions for US roads are defined as:
– lane width =
– lateral clearance =
– design speed ≥
– passenger cars only
– level terrain
Factors affecting capacity
• Roadway conditions
– type of facility and number of lanes
– design speed
– actual lane width and shoulder width
– terrain type: level, rolling, mountainous
• Traffic conditions
– traffic composition (heavy vehicles in traffic)
– type of users
• Control conditions
– traffic interruptions (signs, signals)
– movement restrictions (turn prohibitions)
Sight distance
• Sufficient forward sight distance must be provided
so that drivers can stop to avoid hitting unexpected
obstacles on the road
• Frequent opportunities for safe overtaking should be
provided on 2-lane roads
– this requires longer „passing sight distance”
Stopping sight distance
• Equation for minimum stopping sight distance
(MSSD) in metres:
S = 0.278 V tr +
V is in km/h
tr is in sec (normally assumed 2.0 sec)
f, G are in decimal
• For V = and G = 0 we get:
S = 55.6 + 135.8 = 191.4 m
• Fixing the position of the road in plan
• Horizontal alignment consists of:
– straight segments (tangents)
– circular curves and transition curves
• Main requirements of horizontal alignment are:
– to allow drivers to pass curves comfortably and safely
– to provide adequate sight distance
• Design speed is used as the overall control parameter
– Superelevation is used to resist centrifugal force acting
outwards on a vehicle negotiating a curve
Horizontal alignment
Fixing the position of the road in plan
• Horizontal alignment consists of:
– straight segments (tangents)
– circular curves and transition curves
• Main requirements of horizontal alignment are:
– to allow drivers to pass curves comfortably and safely
– to provide adequate sight distance
• Design speed is used as the overall control parameter
– Superelevation is used to resist centrifugal force acting
outwards on a vehicle negotiating a curve
Vertical alignment
• Maximum gradients and lengths are specified
according to the design speed
• Crest vertical curve
– Radius of a crest vertical curve is governed by
stopping or passing sight distance
• Sag Vertical Curves
– Radius of a sag vertical curve is governed either by:
• Headlight illumination (night visibility) or
• Comfort
• Vertical alignment should be coordinated with
horizontal alignment
Intersections & interchanges
• Types of intersections:
– Intersections at grade
– Grade-separated intersections (interchanges)
• Principles of intersection design
• At-grade Intersections
– uncontrolled (minor roads)
– priority (give-way sign, stop sign)
– roundabouts
– signalised intersections
Roundabouts
• Advantages of roundabouts:
– Orderly one-way traffic movement at low speed
– Elimination of direct crossing conflicts
– Reduction in the number and severity of accidents.
– Suitable especially for multi-leg intersections
• Disadvantages of roundabouts:
– Limited capacity, lower than signalised intersection
– Do not operate well with one movement predominant
– Require a large flat area
– Difficult for pedestrians
Grade-separated intersections(interchanges)
• 3-way interchanges
– trumpet interchange with a single bridge
– Y-shaped directional interchange
• 4-way interchanges
(a) Diamond Interchange
(b) Cloverleaf interchange
(c) Directional Interchange
• Multi-way Interchange
– Various arrangements used
– A roundabout can be used
Acceleration & Deceleration Lanes
• Provided where ramps joint the expressway
• Acceleration Lanes
– Sufficient length must be provided to permit vehicles
to accelerate and merge into the main traffic stream
– The length of acceleration lane is based on:
• ramp entry and exit speed
• gradient of the acceleration lane
• Deceleration Lanes
– Should have sufficient length to permit deceleration
to exit speed
Earthworks
• The process of excavating earth, transporting it and
compacting in another location
– highway earthwork = cutting and filling for the
embankments
– cut and fill are used to maintain a gentle grade
– cut material is used for the embankments
• Mass-haul diagram
– Graph showing the amount of earthwork involved in
highway construction
– used to balance cut and fill
Highway pavements
• Highway pavement = a layered structure meant to:
– support the traffic load
– preserve the structural integrity of the roadway
• Traffic load has to be transferred to subgrade in such
a way that the soil does not permanently deform
• Pavement types:
– flexible pavement – under load pavement deforms
elastically to the same extent as the subgrade
– rigid pavement – consists of slabs which distribute the
load over a large area and deflect minimally
Flexible pavement
• Pavement deflects under wheel load
– deformation is elastic in normal circumstances
– pavement has to withstand resulting stresses
– damage/material fatigue under repetitive loading
– flexible structure allows for contraction-expansion
• Distribution of load through flexible pavement
– main design issue: thickness of pavement structure
– main factor affecting design: subgrade strength
• Other factors:
– traffic load (number of repetitions)
– properties of materials
– climate
Traffic loading
• Only heavy vehicles matter in pavement design
– „fourth power law” – damage to pavement is
proportional to W3.95 cars have practically no effect
• Standard axle load -
– 100 kN/axle (80 kN/axle was used previously)
– Equivalent Standard Axle Load (ESAL)
• Conversion factors for trucks (e.g. UK)
• Pavements are designed for ~20 year life-span
Design traffic loading = number of standard axle load
repetitions over the pavement lifespan
Rigid pavement
• Rigid pavement consists of:
– Portland cement concrete (PCC) slab
– sub-base layer
• Because of slab stiffness, stress in the subgrade is low
• Stresses occur in the slab due to:
– traffic load
– changes in temperature: slab contraction-expansion
– differences between top & bottom temperature:
slab warping, curling
changes in moisture level
Rigid pavement construction
• To control stresses in the slab, rigid pavement is
constructed in segments with joints:
– contraction
– warping
– construction
• Reinforcement (wire mesh) is often provided
• Joints can be: transverse or longitudinal
• Dowel bars are used to facilitate load transfer
• Tie bars are used to restrain movement but allow
for slab rotation (warping joints)
Rigid pavement design
• Design parameters:
– slab thickness
– joint spacing (transverse, longitudinal)
– reinforcement amount
• Factors affecting design:
– traffic loading (ESAL)
– subgrade strength
– concrete strength
– sub-base material properties
Pavement evaluation
• Evaluation of pavement condition:
– roughness (profilometer)
– skid resistance
• Structural evaluation
– measurement of deflection under a wheel load
– conducted in the field with a Benkelman beam
• Surface distress
– visual inspection
– laser equipment
Pavement rehabilitation
• Flexible pavements
– patches, bituminous seal coats
– asphalt concrete overlays
– asphalt concrete recycling (hot or cold mix)
• Rigid pavements
– local surface treatment
– slab replacement
– asphalt concrete overlays
• Pavement Management System (PMS)
– collecting and analyzing pavement data
– selecting cost-effective strategies
Highway Drainage
Highways pose two types of drainage problems:
a) Road surface drainage
– Rainwater collecting on the road must be disposed
off without flooding or damaging the highway and
adjacent areas
b) Cross drainage
– Highways cross many natural drainage channels
– Water must be carried across the road – without
obstructing the flow or causing damage to property
– Cross drainage requires culverts (<6 m span) or
bridges
Need for road surface drainage
• Good drainage of road surface is necessary for:
– Safety and convenience of road users
• water on the road surface may cause skidding
– Protection of adjacent property from damage
– Protection of road pavement
• Components of road surface drainage
– For rural roads - direct overland flow into table drains
– Urban roads - system comprises inlet, kerb, gutter +
roadside drains
Traffic management
• Traffic management = short-term measures to
improve traffic flow on a road network
• Aims of traffic management are:
– safety and efficiency of flow
– limiting negative impacts
• Traffic management measures
– Traffic laws and regulations
– Traffic signs and road markings
– Traffic signals
– Special methods (one-way streets, traffic cells)
– Economic measures (road pricing, parking fees)
Parking control
• Aims to discourage commuters from long-term
parking, by pricing or time restrictions
• Parking control methods
– Regulations – parking is prohibited (by signs)
– Parking meters – fee collection and timing devices,
motorists pay for specific periods of parking
– Parking discs – parking is free but duration is limited
– Coupon parking – which are displayed behind the
windscreen
– Wheel clamps – enforcement measure
Priority for public transport
• Bus lanes - reserved for exclusive use by buses
– Three types of bus lanes:
• With flow curb lanes
• Median bus lanes
• Contraflow lanes
• Bus-only streets
– entire street reserved for exclusive bus use
• Bus priority at intersections
– Detectors in bus cause extension of the green period
– Signal optimisation based on "person delay"
– Phases for bus movements
Traffic signals
• Prevent conflicts by separating traffic flows in time
• Traffic signal terminology
– Traffic signal controller – controls the operation
– Traffic detector – detects the presence of vehicles
– Cycle time – the time period of one complete
sequence of signal indications
– Traffic phase - time allocated to any traffic movement
– Intergreen period - the time between green periods
• Area traffic control systems are used to coordinate
several traffic signals in an area in order to minimise
journey time
Characteristics of rail transport
• Rail systems serve:
– Intercity passenger travel, possibly at high speed
– Regional/commuter rail (40 – 80 km/h)
– Urban rapid mass transport
– Freight transport
• Characteristics:
– freight - high capacity but transit time is high due to
slow terminal operations
– High capital costs, low operating costs
– Relatively low environmental impact
TE – part 15 47
Conventional vs. non-conventional
railways
• Propulsion force is:
– generated inside the vehicle by an on-board engine
– transferred by wheels to the rails by friction
• Guiding (lateral) forces are transferred through
wheel rims
• Examples of non-conventional railways:
– Monorail – train straddles a single rail (beam)
– Cable cars – are suspended from and/or pulled by a cable
– Maglev - magnetic levitation: train is fully supported
by the magnetic force
Railway geometric design
• Similar principles as for highway design but different
parameter values
• Horizontal alignment
– tangents, circular curves – larger radius
– transition curves (cubic parabolas, not spirals)
– superelevation to eliminate centrifugal force: <10%
• Vertical alignment
– gradients much smaller than for road design <2%
– additional effect of friction on a horizontal curve grade
is adjusted down
Overall track structure
• Rails rest on ties and are fixed to them by rail
fastenings (spikes/bolts)
• Ties (sleepers) are embedded in the ballast
• Ballast rests on the subgrade
• Subgrade
Track components – ties
• Functions of ties (sleepers):
– to transmit wheel loads from rails to the ballast
– to maintain constant distance between the two rails
• Tie spacing: 550 – 650 mm
• Typical size: 250 x 150 mm, length: 2.5 m
• Wood used: oak, beech, pine – impregnated
• Prestressed concrete ties - heavier than wood, more
effective in supporting rails
Track components – ballast
• Functions of ballast
– distributing tie loads to the subgrade
– anchoring track against any movement
– providing drainage of water away from rails and ties
– facilitating maintenance: control of alignment
– retarding growth of vegetation
• Depth of ballast: 0.25 – 0.3 m
• Material:
– crushed rock (hard), gravel, slag
• To perform its function, ballast must be properly
compacted under the ties
– this can be done by tamping and vibrating
Stages in railroad construction
• Preparation of the track bed
– earthworks (forming cuts and embankments)
– building of structural objects (bridges, culverts)
– subgrade compaction and alignment
– provision of drainage and traction poles
• Track laying operation (automated or manual)
– Placing ties and rails
– Fixing rails to ties
• Adding ballast
– dropping and spreading ballast
– ballast tamping and adjustment of the rail alignment
Environmental impacts of traffic
• Road traffic produces many undesirable effects:
– noise
– vibrations
– pollution from exhaust fumes
– dust and dirt
– visual intrusion
– accident risk
– severance
– nuisance from parked vehicles
• These issues can be an inconvenience, nuisance or a
danger to health
Noise reduction through road design
• Roads can be designed to minimise the level of
traffic noise in nearby buildings, using:
– vertical alignment which minimises steep gradients
– road in a tunnel or in an open cut
– absorbent ground between road and buildings
– trees and shrubs
– use of pervious surfacing
• Noise barriers
– Barriers should be used as the last resort
– high cost
Characteristics of rail transport
• Rail systems serve:
– Intercity passenger travel, possibly at high speed
– Regional/commuter rail (40 – 80 km/h)
– Urban rapid mass transport
– Freight transport
• Characteristics:
– freight - high capacity but transit time is high due to
slow terminal operations
– High capital costs, low operating costs
– Relatively low environmental impact
Conventional vs. non-conventional
railways
• Propulsion force is:
– generated inside the vehicle by an on-board engine
– transferred by wheels to the rails by friction
• Guiding (lateral) forces are transferred through
wheel rims
• Examples of non-conventional railways:
– Monorail – train straddles a single rail (beam)
– Cable cars – are suspended from and/or pulled by a
cable
– Maglev - magnetic levitation: train is fully supported
by the magnetic force
Railway geometric design
• Similar principles as for highway design but different
parameter values
• Horizontal alignment
– tangents, circular curves – larger radius
– transition curves (cubic parabolas, not spirals)
– superelevation to eliminate centrifugal force: <10%
• Vertical alignment
– gradients much smaller than for road design <2%
– additional effect of friction on a horizontal curve grade
is adjusted down
Overall track structure
• Rails rest on ties and are fixed to them by rail
fastenings (spikes/bolts)
• Ties (sleepers) are embedded in the ballast
• Ballast rests on the subgrade
• Subgrade
Track components – ties
• Functions of ties (sleepers):
– to transmit wheel loads from rails to the ballast
– to maintain constant distance between the two rails• Tie spacing: 550 – 650 mm
• Typical size: 250 x 150 mm, length: 2.5 m
• Wood used: oak, beech, pine – impregnated
• Prestressed concrete ties - heavier than wood, more
effective in supporting rails
Track components – ballast
• Functions of ballast
– distributing tie loads to the subgrade
– anchoring track against any movement
– providing drainage of water away from rails and ties
– facilitating maintenance: control of alignment
– retarding growth of vegetation
• Depth of ballast: 0.25 – 0.3 m
• Material:
– crushed rock (hard), gravel, slag
• To perform its function, ballast must be properly
compacted under the ties
– this can be done by tamping and vibrating
Stages in railroad construction
• Preparation of the track bed
– earthworks (forming cuts and embankments)
– building of structural objects (bridges, culverts)
– subgrade compaction and alignment
– provision of drainage and traction poles
• Track laying operation (automated or manual)
– Placing ties and rails
– Fixing rails to ties
• Adding ballast
– dropping and spreading ballast
– ballast tamping and adjustment of the rail alignment
Environmental impacts of traffic
• Road traffic produces many undesirable effects:
– noise
– vibrations
– pollution from exhaust fumes
– dust and dirt
– visual intrusion
– accident risk
– severance
– nuisance from parked vehicles
• These issues can be an inconvenience, nuisance or a
danger to health
Noise reduction through road design
• Roads can be designed to minimise the level of
traffic noise in nearby buildings, using:
– vertical alignment which minimises steep gradients
– road in a tunnel or in an open cut
– absorbent ground between road and buildings
– trees and shrubs
– use of pervious surfacing
• Noise barriers
– Barriers should be used as the last resort
– high cost
Effects of pollutants
Carbon Monoxide (CO)
Oxides of Nitrogen (NOx)
Oxides of Sulphur (SOx)
Carbon Dioxide (CO2)
Lead Compounds (Pb)
Volatile Organic Compounds (VOC)
Transport accidents
• The most important negative
effect of transport
-worldwide, 1.2 million people are
killed every year
– 10 times more get injured
– social cost: ~ 2% of GDP (500 bln $)
• Accident databases and statistics
– Source: police accident reports
– Analysis of time trends
– International comparisons
– Identification of blackspots
– Effectiveness of countermeasures
Improving road safety
• Combination of measures - 3 E’s:
– Engineering, Education, Enforcement
• Most effective measures:
– wearing of safety belts
– speed reduction
• traffic calming in residential
neighbourhoods,
• speed limits in cities
– strict police enforcement of traffic rules
-traffic education of both motorists and
non-motorists
– minor road engineering improvements
– improved transport facilities for pedestrians
Engineering measures
• Speed reduction
– speed limits at dangerous locations
– traffic calming (humps)
• Roadside improvements
– installation of traffic barriers
– removal of fixed objects (e.g. trees)
• Intersection design
– cross junction roundabouts
– traffic signals
– pedestrian
Crossings