1. p-REES 1: Module 1-E Railway Alignment Design and Geometry
AREMA/FRA Basis
Photos © Michael Loehr 2015

2. AREMA
Mission : The development and advancement of both technical and practical knowledge and recommended practices pertaining to the design, construction and maintenance of railway infrastructure.
Photo © Michael Loehr 2015

3. Federal Railroad Administration (FRA)
The Federal Railroad Administration (FRA) was created by the Department of Transportation Act of 1966.
Mission: The Federal Railroad Administration’s mission is to enable the safe, reliable, and efficient movement of people and goods for a strong America, now and in the future.
Purview: ‘…“general railroad system of transportation” (general system), which is defined as “the network of standard gage track over which goods may be transported throughout the nation.” (49 CFR Part 209, Appendix A)…’

4. Federal Railroad Administration (FRA)
Safety: FRA's Office of Railroad Safety promotes and regulates safety throughout the Nation's railroad industry.
Hazardous Materials  
Motive Power and Equipment
Operating Practices
Signal and Train Control
Track
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5. Tangent Element Length
Length of any track element
Minimum – Based on Alignment, Equipment, Operating Speed, and Truck Centers
Allowable feet is a common value
Preferred - 3 times the velocity in mph. Example Track speed 60 mph, preferred length = 3 X 60 = 180’
Note: Individual railroads and Agencies will have values specific to their system
Photo © Michael Loehr 2015

6. Curvature Railroad Practice Dc = Angle sub-tended by a 100’ Chord Why
( )
Railroad Practice
Chord Definition for Curves
Specified by Degree and expressed as Dc
Dc = Angle sub-tended by a 100’ Chord
Why
Stakeout without tables
Direct Measurement by String Lining without survey
Figure © Michael Loehr 2015

7. Curvature Radius vs Dc cheat sheets Maximum curvature
Design to even Dc not r
Maximum curvature
Freight and Passenger Yards
Dc = 12d 30’ (r = ’)
Coal Loading Loops
Dc = 10d 00’ (r = ’)
New Mainline
Dc = 1d 00’ (r = ’)
Note: 2° 30’ = 2d 30’ this format allows
asci file transmittal
Figure © Michael Loehr 2015

8. 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

9. Spirals Functions Application Reduce lateral and jerk forces
Spirals provide area to runoff superelevation
Application
All curves in Main Tracks
Infrequently used in Yards
Photo © Michael Loehr 2015

10. Spirals AREMA CADD Xo ≅ Ls / 2 Yo ≅ O / 2 10 Chord Clothoid Ls Yo Xo
Figure © Michael Loehr 2015

11. Spirals
Nomenclature
D = degree of circular curve
d = degree of curvature of the spiral at any point
l = Length from the T.S. or S.T., to any point on the spiral having coordinates x and y
s = length l in 100-foot stations
L = total length of spiral
S = length L in 100-foot stations
d = central angle of the spiral from the T.S. or S.T. to any point on the spiral
D = central angle of the whole spiral
a = deflection angle from the tangent at the T.S. or S.T. to any point on the spiral
b = orientation angle from the tangent at any point on the spiral to the T.S. or S.T.
k = increase in degree of curvature per 100-foot station along the spiral
All functions are in feet or degrees unless otherwise noted
Figure © AREMA 2015

12. Spirals
Figure © AREMA 2015

13. Superelevation
Picture Centpacrr at en.wikipedia

14. Superelevation
Figure © AREMA 2015

15. Superelevation Measured and described in Inches Nomenclature
Eq = Equilibrium Elevation
Ea = Elevation Actual
Eu = Elevation Underbalance
Relationships
Eq = Ea + Eu
For Standard Gage Track and Equipment
Eq = V2 Dc
Photo © Wikipedia® 2015

16. Superelevation
Figure © Michael Loehr 2015

17. Superelevation Ea Max Underbalance
Freight uses up to 6” depending on the Railroad
Passenger uses up to 8”
Underbalance
Freight uses 1½” to 2½”
Commuter uses 3” to 4”
Intercity uses 3” to 4”
Photo © Michael Loehr 2015

18. Superelevation Why is Underbalance used?
Not all trains operate at the same speed
To balance rail wear between both rails
To reduce truck hunting by having a net outward force
Reduce plate cutting on wooden ties
Photo © Wikipedia® 2015

19. Superelevation Ea
3 ¼” 63
2° 15’ = 2d 15’
Figure © Michael Loehr 2015

20. Superelevation
Figure © Michael Loehr 2015

21. Grades
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22. Grades Forces from Grades G = rise / run Fg = G * W
1.5% grade, 134 Ton Locomotive
Fg = * 134 = 2.0 tons Fg
rise
run W
Figure © Michael Loehr 2015

23. Grades
Maximum Grades
Steeper grades can be surmounted if they are short
Ice and Leaf oil can limit operations on grades
Freight
0.5% Desirable Maximum
1.5% Typical
Passenger
Matches freight limits typically
Can be 2% to 3% with no freight
Figure © AAR 2015

24. Grades Curve Compensation Application
Curves cause additional drag on the train due to flange friction
Flange forces are increased due to chording of the cars due to tension in the train
Application
Add 0.04% grade for each degree of curve
1% compensated grade desired with 4 degree curve
Actual design grade = 1.0% – (0.04% * 4) = 0.84%
Existing 0.5% grade with a 6 degree curve
Compensated grade = 0.5% + (0.04% * 6) = 0.74%

25. Vertical Curves
The lengths of parabolic vertical curves on Freight, Commuter, and Inter-City Passenger railroads are determined according to AREMA requirements.
Basic Formula
L = D * V2 * 2.15/A
L = length of vertical curve in feet
V = speed of train in mph
A = vertical acceleration in feet/sec2
D = absolute value of the difference in rates of grades (as a decimal)
2.15 = a conversion factor
Freight Design Acceleration - A = 0.10
Passenger Design Acceleration - A = 0.60

26. 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

27. Vertical Curves Design Example - Length L = D * V2 * 2.15/A
Crest Vertical Curve Grade 1 = 1%, Grade 2 = - 0.5%
Freight 50 mph
L = (0.01 – (-0.005)) * (50 * 50) * 2.15/0.10 = ’
Passenger 70 mph
L = (0.01 – (-0.005)) * (70 * 70) * 2.15/0.60 = ’
L = ’, say 825’

28. Vertical Curves Design Example - Elevations
Assume length = 600 feet (6 stations)
D – 0.50 minus – 0.22 = 0.72
R = 0.72/6 = 0.12
Figure © BNSF 2015

29. Clearances Railroad Clearances are Statutory by State
Figure © AREMA 2015

30. Clearances Railroad Clearances also vary by Railroad
Figure © BNSF/UPRR 2015

31. 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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