Post on 06-May-2015
Light Rail Transit Facilities Design Course
Light Rail Alignment Design May 22, 2010
John A. Lackey, PE
Senior Vice President
David Evans and Associates, Inc.
2
Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Discussion Topics
• Design vehicle clearance and loading
• Types of alignments and typical cross sections
– Open track
– In-street alignments
– Adjacent to freight railroads
– Elevated
– Underground
• Alignment Geometry
Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
Light Rail Transit Facilities Design Course
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General Vehicle Characteristics
• Bi-directional • Articulated • Operated as coupled-trains • Three trucks, two axles per truck • Pantograph • High or low floor, or combination
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Accessibility
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Comparison of Light Rail Vehicles
Sample subhead
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
– Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
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Vehicle Loads
•AW0 - Empty vehicle operating weight •AW1 - (Seated load)
– Fully seated passengers + AWO
•AW2 - (Design load) – Standing passengers at 4/m2 + AW1
•AW3 - (Crush load) – Standing passengers at 6/m2 + AW1
•AW4 - (Structure design load) – Standing passengers at 8/m2 + AW1
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Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
– Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
Light Rail Transit Facilities Design Course
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Wheel/Track Relationship
• Vehicle wheel profile
• Rail profile
• -
• Curved track
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Light Rail Transit Facilities Design Course
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Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
– Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
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Vehicle Performance
• Suspension
– Primary
– Secondary
• Other loads affecting performance
– Trucks
– Load leveling
• Performance on alignment
– Accel/decel
– Operating speed
– Track curvature and gradient
– Train size
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
– Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
Light Rail Transit Facilities Design Course
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Dynamic Envelope
• VDE • Other factors:
– Overhang on curves – Lean due to suspension, track superelevation – Track and wheel wear – Wheel/track spacing – Passenger loading
• Maintenance values: – Lateral wheel wear - – Wheel-to-rail side play - – Radial wheel wear -
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Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Design Vehicle Clearance and Loading
– Vehicle characteristics and dimensions
– Vehicle loads
– Wheel/track relationship
– Vehicle performance
– Dynamic envelope
– Guideway clearances
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Guideway Clearances
CE = VDE + OWF + RC
– CE - Clearance Envelope
– VDE - Vehicle Dynamic Envelope
– OWF - Other Wayside Factors
– RC - Running Clearance
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CE = VDE + OWF + RC
OWF = CT + MT + CW
– CT - Construction Tolerance
– MT - Maintenance Tolerance
– CW - Chorded Construction of Walls
• (effects of track curvature and superelevation)
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Guideway Clearances
• CT = allowable deviations from design positions – Track -
– Poles, signal equipment -
– Walls -
• MT = allowable deviations from constructed condition: – Ballasted track -
– Embedded track or Direct Fixation -
– Lateral rail wear -
– Vertical tolerance -
– Cross level variance, ballasted -
– Cross level variance, DF -
• CW = effects of track curvature and superelevation
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Light Rail Transit Facilities Design Course
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CE = VDE + OWF + RC
RC = Running Clearances:
– RC to signals, signs, poles, etc. -
– RC to emergency walkway envelope -
– RC to bridge parapet, walls, other structures -
– -
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Track at Station Platform
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Light Rail Transit Alignment Design Types of Alignments and Typical Cross Sections
– Open Track
– In-Street Alignments
– Adjacent to Freight Railroads
– Elevated
– Underground
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Typical Ballasted Section
Light Rail Transit Facilities Design Course
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Open Track Ballasted
Light Rail Transit Facilities Design Course
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Typical LRT Median
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Open Track Ballasted
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Open Track Direct Fixation (DF)
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Open Track Direct Fixation
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Open Track Direct Fixation
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Light Rail Transit Alignment Design Types of Alignments and Typical Cross Sections
– Open Track
– In-Street Alignments
– Adjacent to Freight Railroads
– Elevated
– Underground
Light Rail Transit Facilities Design Course
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Embedded Track (Paved)
In-Street Alignments
Light Rail Transit Facilities Design Course
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Embedded Track (Paved)
In-Street Alignments
Light Rail Transit Facilities Design Course
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Embedded Track (Paved)
In-Street Alignments
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Light Rail Transit Alignment Design Types of Alignments and Typical Cross Sections
– Open Track
– In-Street Alignments
– Adjacent to Freight Railroads
– Elevated
– Underground
Light Rail Transit Facilities Design Course
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Adjacent to Freight Railroads
Light Rail Transit Facilities Design Course
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Adjacent to Freight Railroads
Light Rail Transit Facilities Design Course
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Adjacent to Freight Railroads Grade Separation
Light Rail Transit Facilities Design Course
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Adjacent to Freight Railroads Grade Separation
Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design Types of Alignments and Typical Cross Sections
– Open Track
– In-Street Alignments
– Adjacent to Freight Railroads
– Elevated
– Underground
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Elevated (Bridges)
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Elevated (Guideway and Station)
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Light Rail Transit Alignment Design Types of Alignments and Typical Cross Sections
– Open Track
– In-Street Alignments
– Adjacent to Freight Railroads
– Elevated
– Underground
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Underground (Tunnel)
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Below Ground - Depressed
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Light Rail Transit Alignment Design
Alignment Geometry
– Design Criteria and Standards
– Horizontal Alignment
– Vertical Alignment
– In-Street Running Impacts and Considerations
– Station Requirements
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Light Rail Transit Alignment Design
Alignment Geometry
– Design Criteria and Standards
– Horizontal Alignment
– Vertical Alignment
– In-Street Running Impacts and Considerations
– Station Requirements
Light Rail Transit Facilities Design Course
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Horizontal Alignment
• Clearances
• Speed
• Tangents
• Circular Curves
• Superelevation
• Spiral Transitions
• Special Track
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Horizontal Alignment
Superelevation
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Horizontal Alignment
Special Track
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Horizontal Alignment
Special Track
– Precurved Rail
•
– Restraining Rail
•
– Emergency Guard Rail
– Turnouts and Crossovers
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Light Rail Transit Alignment Design
Alignment Geometry
– Design Criteria and Standards
– Horizontal Alignment
– Vertical Alignment
– In-Street Running Impacts and Considerations
– Station Requirements
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Vertical Alignment
Profile Grades
Desirable Absolute Condition Maximum Maximum Maximum Mainline Track 3.5% 5.0% 7.0% Stations 0/5% 3.0% 4.5% Yard 0.0% 0.5% 1.0% Storage Track 0.0% 0.25% 0.5%
Minimum grade for drainage = 0.2%
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Vertical Alignment
Vertical Curves
Minimum Length as function of speed: – L = 70 (G1 - G2) for V > 35 – L = 40 (G1 - G2) for 15 < V < 35 – L = 20 (G1 - G2) for V < 15
Minimum length of any vertical curve:
– Desirable – Minimum – Absolute
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Vertical Alignment
Other Considerations
– Station platforms:
• Tangent grade 0 % to 2.0 %
•
– Combined vertical and horizontal curves
•
•
•
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Light Rail Transit Alignment Design
Alignment Geometry
– Design Criteria and Standards
– Horizontal Alignment
– Vertical Alignment
– In-Street Running Impacts and Considerations
– Station Requirements
Light Rail Transit Facilities Design Course
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In-Street Impacts and Considerations
• Operational policies
• Physical and design constraints
• Right-of-Way
Light Rail Transit Facilities Design Course
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Light Rail Transit Alignment Design
Alignment Geometry
– Design Criteria and Standards
– Horizontal Alignment
– Vertical Alignment
– In-Street Running Impacts and Considerations
– Station Requirements
Light Rail Transit Facilities Design Course
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Questions