Vertical Alignment Design A road must be designed to cross some railway tracks. The approaches are both flat, with no horizontal curvature and are at the same level. The vertical alignment comprises a level approach at ground level, a sag curve, a single crest curve over the railway, and a sag curve returning to ground level. The maximum permitted gradient is 6%, and lengths of this gradient may be used between the crest and sag curves if required. The railway tracks are at ground level, and are [W] metres wide. The road alignment must be at least [h] metres above ground level over this entire width. Width of the railway tracks Clearance (height) between rail tracks and alignment W h a) Design the shortest combination of vertical curves using the desirable minimum standards from CD109 - Highway Link Design for a design speed of 60kph. Give your answers in a table with the following headings: Element description Length (m) (hog, sag or gradient) Sag curve K value or Gradient (%) Start Level (m) End Level (m) 0 b) Show how much shorter the alignment could be made if the crest curve is redesigned to one step below desirable minimum K value, but all the other constraints remain the same. Tabulate your answer as in section (a), and state the change in length due to the redesign. Given Data • Width of railway tracks: W (m) • Clearance height: h = 7.8 m • Maximum gradient: 6% = 0.06 ⚫ Design speed: 60 kph • K-values for Vertical Curves: • Sag curve: Ksag = 22 • Crest curve: Kcrest = 79
Vertical Alignment Design A road must be designed to cross some railway tracks. The approaches are both flat, with no horizontal curvature and are at the same level. The vertical alignment comprises a level approach at ground level, a sag curve, a single crest curve over the railway, and a sag curve returning to ground level. The maximum permitted gradient is 6%, and lengths of this gradient may be used between the crest and sag curves if required. The railway tracks are at ground level, and are [W] metres wide. The road alignment must be at least [h] metres above ground level over this entire width. Width of the railway tracks Clearance (height) between rail tracks and alignment W h a) Design the shortest combination of vertical curves using the desirable minimum standards from CD109 - Highway Link Design for a design speed of 60kph. Give your answers in a table with the following headings: Element description Length (m) (hog, sag or gradient) Sag curve K value or Gradient (%) Start Level (m) End Level (m) 0 b) Show how much shorter the alignment could be made if the crest curve is redesigned to one step below desirable minimum K value, but all the other constraints remain the same. Tabulate your answer as in section (a), and state the change in length due to the redesign. Given Data • Width of railway tracks: W (m) • Clearance height: h = 7.8 m • Maximum gradient: 6% = 0.06 ⚫ Design speed: 60 kph • K-values for Vertical Curves: • Sag curve: Ksag = 22 • Crest curve: Kcrest = 79
Traffic and Highway Engineering
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Publisher:Garber, Nicholas J.
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![Vertical Alignment Design
A road must be designed to cross some railway tracks. The approaches are both flat, with no horizontal
curvature and are at the same level. The vertical alignment comprises a level approach at ground level, a
sag curve, a single crest curve over the railway, and a sag curve returning to ground level. The maximum
permitted gradient is 6%, and lengths of this gradient may be used between the crest and sag curves if
required. The railway tracks are at ground level, and are [W] metres wide. The road alignment must be at
least [h] metres above ground level over this entire width.
Width of the railway tracks
Clearance (height) between rail tracks and alignment
W
h
a) Design the shortest combination of vertical curves using the desirable minimum standards from
CD109 - Highway Link Design for a design speed of 60kph. Give your answers in a table with the
following headings:
Element description
Length (m)
(hog, sag or gradient)
Sag curve
K value or
Gradient (%)
Start Level (m)
End Level (m)
0
b) Show how much shorter the alignment could be made if the crest curve is redesigned to one step
below desirable minimum K value, but all the other constraints remain the same. Tabulate your
answer as in section (a), and state the change in length due to the redesign.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc77d576e-0319-4636-bc5a-173808e3c84b%2F4d8359d4-083e-4cf3-b387-1344f0198c1e%2Fnhh0ipc_processed.png&w=3840&q=75)
Transcribed Image Text:Vertical Alignment Design
A road must be designed to cross some railway tracks. The approaches are both flat, with no horizontal
curvature and are at the same level. The vertical alignment comprises a level approach at ground level, a
sag curve, a single crest curve over the railway, and a sag curve returning to ground level. The maximum
permitted gradient is 6%, and lengths of this gradient may be used between the crest and sag curves if
required. The railway tracks are at ground level, and are [W] metres wide. The road alignment must be at
least [h] metres above ground level over this entire width.
Width of the railway tracks
Clearance (height) between rail tracks and alignment
W
h
a) Design the shortest combination of vertical curves using the desirable minimum standards from
CD109 - Highway Link Design for a design speed of 60kph. Give your answers in a table with the
following headings:
Element description
Length (m)
(hog, sag or gradient)
Sag curve
K value or
Gradient (%)
Start Level (m)
End Level (m)
0
b) Show how much shorter the alignment could be made if the crest curve is redesigned to one step
below desirable minimum K value, but all the other constraints remain the same. Tabulate your
answer as in section (a), and state the change in length due to the redesign.
Transcribed Image Text:Given Data
•
Width of railway tracks: W (m)
•
Clearance height: h = 7.8 m
•
Maximum gradient: 6% = 0.06
⚫ Design speed: 60 kph
• K-values for Vertical Curves:
•
Sag curve: Ksag = 22
•
Crest curve: Kcrest = 79
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