Engineering Design Code Urban and Rural Roadway Design
Transcript Of Engineering Design Code Urban and Rural Roadway Design
Urban and Rural Roadway Design
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TDM | ENGINEERING DESIGN CODE
In this chapter
Introduction
5
Objectives & general notes
6
Design standards
8
Design parameters
8
4.1 Design speed
8
4.2 Design vehicles
10
4.3 Visibility for safety
18
4.4 Design for maintenance
23
4.5 Network utilities
23
Geometric alignment
24
5.1 Horizontal alignment
24
5.2 Vertical alignment
25
5.3 Longitudinal gradients
26
Camber, cross-fall and super-elevation 26
6.1 Introduction
26
6.2 Design considerations
27
Standard road configuration
27
7.1 Road reserve and public right of way
27
7.2 Road reserve cross section
28
7.3 Clearance envelopes
28
7.4 Lane widths
30
7.5 Special vehicle lanes
33
7.6 Cycle facilities
33
7.7 Parking
33
7.8 Traffic islands
33
7.9 Medians
34
7.10 Road shoulders
35
7.11 Road safety barrier systems
36
Urban and rural roadway design
7.12 Clear zones 7.13 Cul-de-sac geometry 7.14 Footpaths and berms
Kerb and channel
8.1 Purpose of a kerb and channel 8.2 Design requirements
Vehicle crossings
Intersection design & types
10.1 General principles 10.2 Priority controlled intersections 10.3 Roundabouts 10.4 Signal controlled intersections and crossings 10.5 Grade separation 10.6 References/guidelines
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TDM | ENGINEERING DESIGN CODE
Urban and rural roadway design
01
PURPOSE
DEPARTURES ROADS AND STREETS FRAMEWORK (RASF)
URBAN STREET AND ROAD DESIGN GUIDE (USRDG)
Introduction
The geometric design of the urban street and rural road networks is important to ensure that correct operation at the right road speed occurs in a safe and predictable manner. Design constraints will vary between projects, especially those within the rural urban boundary, but the general principles behind good road design do not change. The purpose of this chapter is to provide guidance on the issues that need to be considered when dealing with road geometry in Auckland, whether it is a new project or a retrofit of an existing road.
Street users should be able to observe the road environment, decide on safe speed and path to follow, and act upon that. When interacting with other users, they should be able to observe them, predict their likely action, decide on their response, and act. Geometric design should provide enough time for safe decisions and actions.
Where any deviations from the standards are necessary, they must be clearly documented and must follow the AT Departures from Standard process.
The Framework sets out the process for planning or altering a transport network.
It provides guidance on the strategic types of street and the functions and features to be expected in each street, together with modal priorities.
It also describes the process for resolving conflicts for priorities. This should be used to resolve the common issues around general traffic provision with other modes of transport.
This sets out principles for design of the various street types.
Chapter 1 Design Principles These principles must be understood by all designers as the basis for decisions, and the approach to be taken in the design process. In particular, this sets out how safety must be incorporated in all design work.
Chapter 2 Neighbourhood Design focuses on design aspects of planned networks, either as a means of designing the relationship between land use and movement, or for evaluating the local design context for a specific street or place within a neighbourhood. It also includes guidance on environmental design within a neighbourhood.
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RURAL ROADS DESIGN GUIDE FOOTPATHS AND
THE PUBLIC REALM CYCLING INFRASTRUCTURE
02
IMPACTS OF ROAD DESIGN
FOCUS
Chapter 3 Street Users takes each user group in turn, and describes their needs, specific design principles and the features that can be provided for them. Having understood principles and context, this chapter guides the choice of elements for each user to meet the planned function.
Chapter 4 Design Controls deals with the issues of geometric design that need to be considered, to ensure that drivers of vehicles in particular are guided to behave reliably in the way planned for them, safely and efficiently.
Chapter 5 Street Types and
Chapter 6 Intersections can then be used to put the elements together in accordance with the design principles into street and intersection layouts that will effectively deliver the planned outcomes. Typical layouts are shown, not as finished designs, but to illustrate the design considerations required to fit elements together into the design of a whole place.
This is to be developed later, to set principles for design of the various rural road types.
The Engineering Design Code - Footpaths and the Public Realm should be used with this chapter to fully define the overall road cross section. The two documents overlap along the kerb zone boundary with the Engineering Design Code - Footpath and the Public Realm acting as an overlay when providing for pedestrians crossing the roadway
The Engineering Design Code - Cycling infrastructure deals with people on bikes within roadway and footpath and the public realm and is to be used along with these Codes.
Objectives & general notes
The geometric design of roads has a direct impact on the following: • Urban or rural amenity; • Road Safety; • Drainage Design; • Environmental Impact; • Material quantities and construction costs; • Operation and Operational Capacity; and • Maintenance.
The design standards generally contained in most roading standards have traditionally been focused with road safety in mind and to provide for safe operation at the various design speeds. With the release of the Auckland Plan, a vision of a compact city has been established and as such built form and amenity of the environment is to be considered alongside safety and operation.
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TDM | ENGINEERING DESIGN CODE
Urban and rural roadway design
PROVISION FOR ROAD DRAINAGE ENVIRONMENTAL IMPACTS
MATERIAL QUANTITIES AND CONSTRUCTION COSTS
DESIGN FOR OPERATION
DESIGN FOR MAINTENANCE
The geometric design (and any subsequent alterations) affects the ability for the road to provide adequate drainage for surface water. It is important to consider the effect of flooding from any neighbouring watercourses and fix the vertical alignment of the carriageway at an appropriate level.
The horizontal and vertical alignment of a road has an impact on the surrounding environment. Visual and noise impacts often depend on the elevation of the road, as much as the choice of surfacing material. The alignment also has an impact on the number of construction vehicles required to deliver or remove material from the site and therefore the impact on the local communities.
The quantity of material required to be imported, excavated or moved has a direct impact on the costs required to construct the new alignment. Geometry has the largest impact on the requirement for material use and poor alignments, road widths or elevation can increase the costs substantially.
The design of the roadway and its alignment including intersection spacing and methods of control play a significant role in the safe operational performance of vehicles as well as the capacity of the roadway.
It is imperative that roadways and the supporting movement environments are designed in such a way as to reduce impacts on the surrounding land whilst achieving the movement objectives as defined in the Roads and Streets Framework.
On high movement corridors, the focus may be on efficiency of movement and improving capacity or travel times of various modes safely, while environments with a high place value may require capacity or speed reductions to ensure that people on foot or bike are kept safe.
It is critical when designing the roadway infrastructure to consider how maintenance of the road environment can be achieved in a safe and cost effective manner that reduces the requirements for traffic management and its associated costs and disruption.
The road or street must remain safe and usable for all modes while maintaining the network, therefore maintenance requirements should be built in to the design to ensure that this can occur.
Early engagement with Auckland Transport’s maintenance teams is necessary to develop a correct methodology that can be incorporated in to the design.
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03
ROADS & STREETS FRAMEWORK TDM DESIGN TOOL BOX
DESIGN STANDARDS FOR GEOMETRIC DESIGN
IN NEW ZEALAND
OTHER DOCUMENTS OCCASIONALLY USED
04
MAXIMUM SAFE SPEED DETERMINING FACTORS
DESIGN SPEED VS. SPEED LIMIT
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TDM | ENGINEERING DESIGN CODE
Design standards
This should be used to determine the street type, and the characteristics required, in order to set Design parameters. AT publishes various design aids in the TDM Design Tool Box. These are to be used in all roadway design. They include CAD tools such as Design Vehicle profiles, software settings for vehicle tracking, templates for turning heads and intersection corners. These Tools describe and embed the design rules of this Code. The rules and requirements contained in this code will take precedence over any other standard unless agreed by departure, however the following geometric standards and advice notes may be used to supplement this code: Austroads Guide to Road Design: • Part 1 Introduction to Road Design • Part 2 Design Considerations • Part 3 Geometric Design • Part 4B Roundabouts Other documents that are sometimes needed are: Austroads Guide to Road Design Part 6A: Pedestrian and Cyclist Paths Austroads Guide to Traffic Management New Zealand Heavy Haulage Association (NZHHA) Road Design Specifications for Over-dimensional Loads
Design parameters
4.1 Design speed
The design speed of a road is the maximum speed at which a vehicle can safely travel on that road under good conditions. The design speed is based on the: • road and street type* (see Roads and Streets Framework) • conditions of the road itself • conditions of the surrounding land • maximum speed allowed by law • volume of traffic • operating speed of the road, i.e. how fast traffic actually goes.
* In greenfield situations the road types shall be as agreed through the structure plan or precinct plan for the land in question in conjunction with the Roads and Streets Framework.
In the urban environment, as defined by the Auckland Unitary Plan and in accordance with network plans and Streets Typologies, the design speed of the road shall be the same or less than the intended speed limit of the street.
Urban and rural roadway design
AUSTROADS GUIDES CONSISTENCY
URBAN ROAD SPEED MANAGEMENT
NOT ALL VEHICLES ROAD SIDE INFRASTRUCTURE
For rural roads or high speed urban roads with intended speed limit >60km/h, the 85th percentile speed shall be used with the design speed being 10km/h higher for the posted speed checks.
However, for rural roads, geometry should be determined to maintain a consistency along lengths of a particular type and character.
This design speed is used for alignment and intersection design. A higher operating speed may need to be used for safetyrelated design checks (see Section 4.3). This includes:
• Sight distances
• Clear zones
• Safety barriers
• Separation between users (eg. Buffer width between traffic lane and footpath or cycle lane, flush median and turning bays)
Section 3 of the Austroads 2010 Guide to Road Design Part 3: Geometric Design contains detailed information on the assessment of the 85th percentile speeds and how it can be derived for rural and urban environments.
Roads have to be geometrically consistent, so that drivers can negotiate them safely. If geographical constraints, road alignments or the environment cause the operating speed to vary along the road, the design speed has to change accordingly. These changes in speed have to be consistent with normal driver expectations and capability, otherwise drivers will not be able to react in time.
The design of the whole road environment (horizontal alignment, intersection spacing and control, adjoining land use and street activity, speed management features) should combine to present vehicle drivers with a consistent expectation and through this a desired speed not greater than the design speed.
Changes should be evident and should not be concealed by features, such as sharply-decreasing radius within a bend or by a crest curve.
Where the intended Operating Speed is to be kept low for safety and urban design environment, care needs to be taken that the combination of road geometry and operating conditions can ensure that the Operating Speed does not exceed the intended speed. If this is demonstrated consistently, the Design Speed may be reduced below 50 km/h.
Design speed does not cover all vehicles on the road, e.g. cars can travel faster than tractor-trailers. In some areas, e.g. with steep hills or sharp curves, a slower operating speed may apply to tractor-trailers. When designing such a road, take care to allow faster vehicles to safely overtake slower ones.
When proposing infrastructure that vehicles might conflict with, designers have to consider the interaction between operating speeds, visibility and stopping distances and survivable speed.
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DEFINITION PURPOSE
TURNING SPEED
MANOEUVRE SPEED ACCELERATION AND DECELERATION (BUSES) SWEPT PATH WIDTH
TRACKING PROFILES
BUSES FREIGHT, OVER DIMENSIONAL
AND OVERWEIGHT ROUTES
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TDM | ENGINEERING DESIGN CODE
4.2 Design vehicles
Design vehicles are selected motor vehicles with the weight, dimensions, and operating characteristics used to establish highway design controls for accommodating vehicles of designated classes.
The Design Vehicle is used for the purposes of geometric design to ensure that the alignment is suited to the expected vehicle class.
RTS 18:2005 is not to be used for Urban or Rural roads in the Auckland Region. The guidance contained in this document must be used instead.
Swept path analyses for intersections must be run using a turning speed appropriate to the context. The setting that permits steering while the vehicle is stationary may not be used.
Turning speed for buses and Check vehicles should generally be in the range of 5-25 km/h, giving regard to road design speed differential and desirable deceleration to the speed for the turn.
For roads with design speed greater than 50 km/h, turning speed may be increased where deceleration lane space cannot be provided and no conflict with people on foot or on bikes will occur.
High differential between turning speed and through traffic speed can be a significant safety risk. The design turning speed should correlate with the operating speed. For example, at an intersection on a 60km/h arterial road, the design turning speed may be 25km/h.
Some manoeuvres such as parking, reverse turning or using vehicle crossings will require a lower swept path speed than intersections. Manoeuvre speed down to 3 km/h may be used.
Particular care needs to be taken with tracking speed when approaching or exiting bus stops noting that the vehicle is likely to be decelerating or accelerating. The turning speed used for tracking needs to account for this.
The path for design shall be the body width of the vehicle, plus 0.5 m clearance to allow for projections and variability in actual vehicle paths. Clearance shall be from an adjacent traffic lane or the face of a kerb (and may include a kerbside channel).
The design and check vehicle profiles can be downloaded from the Transport Design Manual home page. Software settings for intersection and manouevre design should be in accord with AT Design Tools guidance.
Bus tracking must use all standard AT bus types as defined as per the tracking profiles above in each instance where a road is or could be used by buses.
Where the road is part of a freight, over-dimensional or overweight route it is a requirement that tracking be undertaken to show the effect this will have on any proposed design. All freight routes, whatever street type, require 19.45 m semi as Design Vehicle and 23m truck & trailer as Check vehicle.
01 02 03 04
05
06 07
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TDM | ENGINEERING DESIGN CODE
In this chapter
Introduction
5
Objectives & general notes
6
Design standards
8
Design parameters
8
4.1 Design speed
8
4.2 Design vehicles
10
4.3 Visibility for safety
18
4.4 Design for maintenance
23
4.5 Network utilities
23
Geometric alignment
24
5.1 Horizontal alignment
24
5.2 Vertical alignment
25
5.3 Longitudinal gradients
26
Camber, cross-fall and super-elevation 26
6.1 Introduction
26
6.2 Design considerations
27
Standard road configuration
27
7.1 Road reserve and public right of way
27
7.2 Road reserve cross section
28
7.3 Clearance envelopes
28
7.4 Lane widths
30
7.5 Special vehicle lanes
33
7.6 Cycle facilities
33
7.7 Parking
33
7.8 Traffic islands
33
7.9 Medians
34
7.10 Road shoulders
35
7.11 Road safety barrier systems
36
Urban and rural roadway design
7.12 Clear zones 7.13 Cul-de-sac geometry 7.14 Footpaths and berms
Kerb and channel
8.1 Purpose of a kerb and channel 8.2 Design requirements
Vehicle crossings
Intersection design & types
10.1 General principles 10.2 Priority controlled intersections 10.3 Roundabouts 10.4 Signal controlled intersections and crossings 10.5 Grade separation 10.6 References/guidelines
38 38 39
39
08
39
40
42
09
45
10
45
48
49
50
52
52
3
4
TDM | ENGINEERING DESIGN CODE
Urban and rural roadway design
01
PURPOSE
DEPARTURES ROADS AND STREETS FRAMEWORK (RASF)
URBAN STREET AND ROAD DESIGN GUIDE (USRDG)
Introduction
The geometric design of the urban street and rural road networks is important to ensure that correct operation at the right road speed occurs in a safe and predictable manner. Design constraints will vary between projects, especially those within the rural urban boundary, but the general principles behind good road design do not change. The purpose of this chapter is to provide guidance on the issues that need to be considered when dealing with road geometry in Auckland, whether it is a new project or a retrofit of an existing road.
Street users should be able to observe the road environment, decide on safe speed and path to follow, and act upon that. When interacting with other users, they should be able to observe them, predict their likely action, decide on their response, and act. Geometric design should provide enough time for safe decisions and actions.
Where any deviations from the standards are necessary, they must be clearly documented and must follow the AT Departures from Standard process.
The Framework sets out the process for planning or altering a transport network.
It provides guidance on the strategic types of street and the functions and features to be expected in each street, together with modal priorities.
It also describes the process for resolving conflicts for priorities. This should be used to resolve the common issues around general traffic provision with other modes of transport.
This sets out principles for design of the various street types.
Chapter 1 Design Principles These principles must be understood by all designers as the basis for decisions, and the approach to be taken in the design process. In particular, this sets out how safety must be incorporated in all design work.
Chapter 2 Neighbourhood Design focuses on design aspects of planned networks, either as a means of designing the relationship between land use and movement, or for evaluating the local design context for a specific street or place within a neighbourhood. It also includes guidance on environmental design within a neighbourhood.
5
RURAL ROADS DESIGN GUIDE FOOTPATHS AND
THE PUBLIC REALM CYCLING INFRASTRUCTURE
02
IMPACTS OF ROAD DESIGN
FOCUS
Chapter 3 Street Users takes each user group in turn, and describes their needs, specific design principles and the features that can be provided for them. Having understood principles and context, this chapter guides the choice of elements for each user to meet the planned function.
Chapter 4 Design Controls deals with the issues of geometric design that need to be considered, to ensure that drivers of vehicles in particular are guided to behave reliably in the way planned for them, safely and efficiently.
Chapter 5 Street Types and
Chapter 6 Intersections can then be used to put the elements together in accordance with the design principles into street and intersection layouts that will effectively deliver the planned outcomes. Typical layouts are shown, not as finished designs, but to illustrate the design considerations required to fit elements together into the design of a whole place.
This is to be developed later, to set principles for design of the various rural road types.
The Engineering Design Code - Footpaths and the Public Realm should be used with this chapter to fully define the overall road cross section. The two documents overlap along the kerb zone boundary with the Engineering Design Code - Footpath and the Public Realm acting as an overlay when providing for pedestrians crossing the roadway
The Engineering Design Code - Cycling infrastructure deals with people on bikes within roadway and footpath and the public realm and is to be used along with these Codes.
Objectives & general notes
The geometric design of roads has a direct impact on the following: • Urban or rural amenity; • Road Safety; • Drainage Design; • Environmental Impact; • Material quantities and construction costs; • Operation and Operational Capacity; and • Maintenance.
The design standards generally contained in most roading standards have traditionally been focused with road safety in mind and to provide for safe operation at the various design speeds. With the release of the Auckland Plan, a vision of a compact city has been established and as such built form and amenity of the environment is to be considered alongside safety and operation.
6
TDM | ENGINEERING DESIGN CODE
Urban and rural roadway design
PROVISION FOR ROAD DRAINAGE ENVIRONMENTAL IMPACTS
MATERIAL QUANTITIES AND CONSTRUCTION COSTS
DESIGN FOR OPERATION
DESIGN FOR MAINTENANCE
The geometric design (and any subsequent alterations) affects the ability for the road to provide adequate drainage for surface water. It is important to consider the effect of flooding from any neighbouring watercourses and fix the vertical alignment of the carriageway at an appropriate level.
The horizontal and vertical alignment of a road has an impact on the surrounding environment. Visual and noise impacts often depend on the elevation of the road, as much as the choice of surfacing material. The alignment also has an impact on the number of construction vehicles required to deliver or remove material from the site and therefore the impact on the local communities.
The quantity of material required to be imported, excavated or moved has a direct impact on the costs required to construct the new alignment. Geometry has the largest impact on the requirement for material use and poor alignments, road widths or elevation can increase the costs substantially.
The design of the roadway and its alignment including intersection spacing and methods of control play a significant role in the safe operational performance of vehicles as well as the capacity of the roadway.
It is imperative that roadways and the supporting movement environments are designed in such a way as to reduce impacts on the surrounding land whilst achieving the movement objectives as defined in the Roads and Streets Framework.
On high movement corridors, the focus may be on efficiency of movement and improving capacity or travel times of various modes safely, while environments with a high place value may require capacity or speed reductions to ensure that people on foot or bike are kept safe.
It is critical when designing the roadway infrastructure to consider how maintenance of the road environment can be achieved in a safe and cost effective manner that reduces the requirements for traffic management and its associated costs and disruption.
The road or street must remain safe and usable for all modes while maintaining the network, therefore maintenance requirements should be built in to the design to ensure that this can occur.
Early engagement with Auckland Transport’s maintenance teams is necessary to develop a correct methodology that can be incorporated in to the design.
7
03
ROADS & STREETS FRAMEWORK TDM DESIGN TOOL BOX
DESIGN STANDARDS FOR GEOMETRIC DESIGN
IN NEW ZEALAND
OTHER DOCUMENTS OCCASIONALLY USED
04
MAXIMUM SAFE SPEED DETERMINING FACTORS
DESIGN SPEED VS. SPEED LIMIT
8
TDM | ENGINEERING DESIGN CODE
Design standards
This should be used to determine the street type, and the characteristics required, in order to set Design parameters. AT publishes various design aids in the TDM Design Tool Box. These are to be used in all roadway design. They include CAD tools such as Design Vehicle profiles, software settings for vehicle tracking, templates for turning heads and intersection corners. These Tools describe and embed the design rules of this Code. The rules and requirements contained in this code will take precedence over any other standard unless agreed by departure, however the following geometric standards and advice notes may be used to supplement this code: Austroads Guide to Road Design: • Part 1 Introduction to Road Design • Part 2 Design Considerations • Part 3 Geometric Design • Part 4B Roundabouts Other documents that are sometimes needed are: Austroads Guide to Road Design Part 6A: Pedestrian and Cyclist Paths Austroads Guide to Traffic Management New Zealand Heavy Haulage Association (NZHHA) Road Design Specifications for Over-dimensional Loads
Design parameters
4.1 Design speed
The design speed of a road is the maximum speed at which a vehicle can safely travel on that road under good conditions. The design speed is based on the: • road and street type* (see Roads and Streets Framework) • conditions of the road itself • conditions of the surrounding land • maximum speed allowed by law • volume of traffic • operating speed of the road, i.e. how fast traffic actually goes.
* In greenfield situations the road types shall be as agreed through the structure plan or precinct plan for the land in question in conjunction with the Roads and Streets Framework.
In the urban environment, as defined by the Auckland Unitary Plan and in accordance with network plans and Streets Typologies, the design speed of the road shall be the same or less than the intended speed limit of the street.
Urban and rural roadway design
AUSTROADS GUIDES CONSISTENCY
URBAN ROAD SPEED MANAGEMENT
NOT ALL VEHICLES ROAD SIDE INFRASTRUCTURE
For rural roads or high speed urban roads with intended speed limit >60km/h, the 85th percentile speed shall be used with the design speed being 10km/h higher for the posted speed checks.
However, for rural roads, geometry should be determined to maintain a consistency along lengths of a particular type and character.
This design speed is used for alignment and intersection design. A higher operating speed may need to be used for safetyrelated design checks (see Section 4.3). This includes:
• Sight distances
• Clear zones
• Safety barriers
• Separation between users (eg. Buffer width between traffic lane and footpath or cycle lane, flush median and turning bays)
Section 3 of the Austroads 2010 Guide to Road Design Part 3: Geometric Design contains detailed information on the assessment of the 85th percentile speeds and how it can be derived for rural and urban environments.
Roads have to be geometrically consistent, so that drivers can negotiate them safely. If geographical constraints, road alignments or the environment cause the operating speed to vary along the road, the design speed has to change accordingly. These changes in speed have to be consistent with normal driver expectations and capability, otherwise drivers will not be able to react in time.
The design of the whole road environment (horizontal alignment, intersection spacing and control, adjoining land use and street activity, speed management features) should combine to present vehicle drivers with a consistent expectation and through this a desired speed not greater than the design speed.
Changes should be evident and should not be concealed by features, such as sharply-decreasing radius within a bend or by a crest curve.
Where the intended Operating Speed is to be kept low for safety and urban design environment, care needs to be taken that the combination of road geometry and operating conditions can ensure that the Operating Speed does not exceed the intended speed. If this is demonstrated consistently, the Design Speed may be reduced below 50 km/h.
Design speed does not cover all vehicles on the road, e.g. cars can travel faster than tractor-trailers. In some areas, e.g. with steep hills or sharp curves, a slower operating speed may apply to tractor-trailers. When designing such a road, take care to allow faster vehicles to safely overtake slower ones.
When proposing infrastructure that vehicles might conflict with, designers have to consider the interaction between operating speeds, visibility and stopping distances and survivable speed.
9
DEFINITION PURPOSE
TURNING SPEED
MANOEUVRE SPEED ACCELERATION AND DECELERATION (BUSES) SWEPT PATH WIDTH
TRACKING PROFILES
BUSES FREIGHT, OVER DIMENSIONAL
AND OVERWEIGHT ROUTES
10
TDM | ENGINEERING DESIGN CODE
4.2 Design vehicles
Design vehicles are selected motor vehicles with the weight, dimensions, and operating characteristics used to establish highway design controls for accommodating vehicles of designated classes.
The Design Vehicle is used for the purposes of geometric design to ensure that the alignment is suited to the expected vehicle class.
RTS 18:2005 is not to be used for Urban or Rural roads in the Auckland Region. The guidance contained in this document must be used instead.
Swept path analyses for intersections must be run using a turning speed appropriate to the context. The setting that permits steering while the vehicle is stationary may not be used.
Turning speed for buses and Check vehicles should generally be in the range of 5-25 km/h, giving regard to road design speed differential and desirable deceleration to the speed for the turn.
For roads with design speed greater than 50 km/h, turning speed may be increased where deceleration lane space cannot be provided and no conflict with people on foot or on bikes will occur.
High differential between turning speed and through traffic speed can be a significant safety risk. The design turning speed should correlate with the operating speed. For example, at an intersection on a 60km/h arterial road, the design turning speed may be 25km/h.
Some manoeuvres such as parking, reverse turning or using vehicle crossings will require a lower swept path speed than intersections. Manoeuvre speed down to 3 km/h may be used.
Particular care needs to be taken with tracking speed when approaching or exiting bus stops noting that the vehicle is likely to be decelerating or accelerating. The turning speed used for tracking needs to account for this.
The path for design shall be the body width of the vehicle, plus 0.5 m clearance to allow for projections and variability in actual vehicle paths. Clearance shall be from an adjacent traffic lane or the face of a kerb (and may include a kerbside channel).
The design and check vehicle profiles can be downloaded from the Transport Design Manual home page. Software settings for intersection and manouevre design should be in accord with AT Design Tools guidance.
Bus tracking must use all standard AT bus types as defined as per the tracking profiles above in each instance where a road is or could be used by buses.
Where the road is part of a freight, over-dimensional or overweight route it is a requirement that tracking be undertaken to show the effect this will have on any proposed design. All freight routes, whatever street type, require 19.45 m semi as Design Vehicle and 23m truck & trailer as Check vehicle.