1. p-REES 1: Module 1-F Railway Alignment Design and Geometry
APTA/TCRP/FTA Basis
Photos © Michael Loehr 2015

2. APTA
Mission : To strengthen and improve public transportation, APTA serves and leads its diverse membership through advocacy, innovation and information sharing. APTA and its members and staff work to ensure that public transportation is available and accessible for all Americans in communities across the country.
Photo © Michael Loehr 2015

3. TRB / TCRP
TRB Mission : The mission of the Transportation Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal
TCRP Mission : The Transit Cooperative Research Program is an applied, contract research program that develops near-term, practical solutions to problems facing transit agencies.

4. Federal Transit Administration (FTA)
President Lyndon Johnson signed the Urban Mass Transportation Act into law on July 9, The new measure provided $375 million in capital assistance over three years. It passed the House by a vote of 212- to-129 and cleared the Senate
“We are a nation of travelers. You cannot write our history without devoting many chapters to the pony express, the stagecoach, the railroad, the automobile, the airplane. . . Yet, until 1964, the Federal Government did little or nothing to help the urban commuter.” – President Lyndon B. Johnson, on Remarks at the Signing of the Urban Mass Transportation Act
Mission: To ensure personal mobility and America's economic and community vitality by supporting high quality public transportation through leadership, technical assistance and financial resources..
Purview: ‘Public transportation includes buses, subways, light rail, commuter rail, monorail, passenger ferry boats, trolleys, inclined railways, and people movers. The federal government, through the FTA, provides financial assistance to develop new transit systems and improve, maintain, and operate existing systems. The FTA oversees grants to state and local transit providers…’

5. Federal Transit Administration (FTA)
Oversight: FTA defines oversight as a continuous review and evaluation of grantee and FTA processes to ensure compliance with statutory, administrative, and regulatory requirements. The Office of Engineering, through the Regional Offices, performs oversight of grantee project management that focuses on the management of major investments (New Starts, rail modernization, etc.) in transit projects. This activity begins early in project implementation, usually at the time of preliminary engineering. PMO contractors monitor the large caseload of projects, following guidelines established by FTA. They serve to supplement the FTA technical staff to evaluate grantee project management and technical capacity and capability to successfully implement these major transit projects. They also monitor the projects to determine whether they are progressing on time, within budget, and in accord with approved grantee plans and specifications. Other activities are also involved, such as reviews of whether a given design can in fact be constructed, change order reviews, and value engineering.

6. TCRP 57 and TCRP 155
TCRP Track Design Handbook for Light Rail Transit 2nd Edition
TCRP 155 updates TCRP 57, but refers back to the original document.
Photo © Michael Loehr 2015

7. Tangent Element Length
Length of any track element
Minimum – Based on Alignment, Equipment, Operating Speed, and Truck Centers
Preferred - 3 times the velocity in mph. Example Track speed 60 mph, preferred length = 3 X 60 = 180’
Note: Individual Transit Agencies will have values specific to their system
Photo © Michael Loehr 2015

8. Curvature Transit Practice Dc = Angle sub-tended by a 100’ Arc Why
Arc Definition for Curves
Specified by Radius
Dc = Angle sub-tended by a 100’ Arc
Why
Matches Highway practices
Very small radii compared to railroads
Figure © Michael Loehr 2015

9. Curvature Minimum Radius Passenger Yards Embedded Track New Mainline
r = 82’ (25m)
Embedded Track
New Mainline
r = 500’ (150m)
Photo © Michael Loehr 2015

10. Spirals Spirals provide smooth transition from tangents to curves
Sometimes used in Highway Design, but not common practice
Straight Entering Curve Full Curve
Figure © Michael Loehr 2015

11. Spirals Functions Application Reduce lateral and jerk forces
Spirals provide area to runoff superelevation
Application
Spirals should be used on all main line track horizontal curves with radii less than 10,000 feet.
Spirals can be omitted if the calculated length of spiral (Ls) is less than 0.01R
Infrequently used in Yards

12. Spirals LRT CADD k ≅ Ls / 2 Yo ≅ p / 2 Hickerson Clothoid p k Ls Yo
Figure © Michael Loehr 2015

13. Spirals
Figure TCRP 155

14. Spirals
Figure TCRP 155

15. Spirals
Figure from TCRP 155

16. Superelevation
Picture © Michael Loehr 2015

17. Superelevation
Figure © AREMA 2015

18. Superelevation Measured and described in Inches Nomenclature
Eq = Equilibrium Elevation
Ea = Elevation Actual
Eu = Elevation Underbalance
Er = Elevation Body Roll
Er typically included in Eu
Ec = Comfort Elevation
Photo © Wikipedia® 2015

19. Superelevation Relationships Eq = Ea + Eu + Er Ec = Eq – Er = Ea + Eu
For Standard Gage Track and Equipment
Eq = 4.0 V2 / R
Eu = 0.82 Ea – 0.4
Ea = 2.18 (V2 / R) – 0.22
V in Miles per Hour
R in Feet
E in Inches
Figure TCRP 155

20. Superelevation Ea Max Underbalance Varies by Agency Typical 6”
Photo © Michael Loehr 2015

21. Superelevation
Maximum Speed
Figure © Michael Loehr 2015

22. Superelevation Overturning Unbalance Superelevation
The formula for computing superelevation unbalance for ‘Overturning Speed Eu’ is derived from the theory of superelevation:
Eu for Overturning = Be/h Eu in inches
Where;
B = rail bearing distance in inches
e = B/2 – x (to determine overturning)
h = height of center of gravity in inches

23. Superelevation Overturning Speed
The following formula is generalized to allow its use with any track gage. V is in mph, R is in Feet, and Eu is calculated by the preceding equation.
Overturning V = 𝐸𝑎+𝐸𝑢 ∗ 𝑅 ∗ 𝐵

24. Superelevation Why is Underbalance used?
To balance rail wear between both rails
To reduce truck hunting by having a net outward force
Ride quality
Photo © Wikipedia® 2015

25. Grades
Maximum Grades
Steeper grades can be surmounted if they are short
Ice and Leaf oil can limit operations on grades
Light Rail Passenger
Maintenance equipment
may limit maximum grade
Can be 7% to 9%
Figure © NJTransit 2015

26. Vertical Curves
The minimum length of vertical curves can be determined as follows:
Desired Minimum Length: LVC = 200A
Acceptable Minimum Length: LVC = 100A
where
LVC = length of vertical curve in feet
A = (G2 – G1) algebraic difference in gradients in percent
G1 = percent grade of approaching tangent
G2 = percent grade of departing tangent
V = design speed in mph

27. Vertical Curves
The minimum length of vertical curves can be determined as follows:
Absolute Minimum Length:

28. Vertical Curve
A parabola is used for the vertical curve in which the correction from the straight grade for the first station is one half the rate of change, and the others vary as the square of the distance from the point of tangency. Where points fall on full stations, it will be necessary to figure these for only one half the vertical curve, as they are the same for corresponding points each side of the vertex. Corrections are (-) when the vertical curve is concave downwards (summit), and (+) when the vertical curve is concave upwards (sag).
The rate of change per station is calculated as follows: R = D/L
Where:
R = Rate of change per station
D = Algebraic difference of the two intercepting grades
L = Length of vertical curve in 100-ft. stations
M = Correction from the straight grade to the vertical curve
Figure © BNSF 2015

29. Vertical Curves
Light Rail Vehicles have capabilities for vertical curves rated based on radius
The equivalent radius of curvature can be calculated from the following formula:

30. Clearances Light Rail Clearances may be Statutory by State
The track clearance envelope (TCE) is defined as the space occupied by the maximum vehicle dynamic envelope (VDE) as defined in TCRP 155 Chapter 2, Article 2.3, plus effects due to curvature and superelevation, construction and maintenance tolerances of the track structure, construction tolerances of adjacent wayside structures, and running clearances. The relationship between the vehicle and clearance envelopes can thus be expressed as follows:
TCE = VDE + TT + C&S + RC
where
TCE = track clearance envelope
VDE = vehicle dynamic envelope
TT = trackwork construction and maintenance tolerances
C&S = vehicle curve and superelevation effects
RC = vehicle running clearance

31. Clearances
The following items are typically included in the development of the Vehicle Dynamic Envelope:
Static vehicle outline
Dynamic motion (roll) of springs and suspension/bolsters of vehicle trucks
Vehicle suspension side play and component wear
Vehicle wheel flange and radial tread wear
Maximum truck yaw (fishtailing)
Maximum passenger loading
Suspension system failure
Wheel and track nominal gauge difference
Wheel back-to-back mounting and maintenance tolerance
Figure from TCRP 155

32. Clearances
Horizontal offsets for LRV car bodies are important considerations because of the smaller radii.
Figure from TCRP 155

33. Michael Loehr Practice Leader Rail & Transit – Americas - Civil
Transportation Business Group
CH2M HILL
8720 Stony Point Parkway, Suite 110
Richmond, VA
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