Lecture 5, Tues Feb 13,2018 and Thurs,Feb 15/// Lecture 5 on moodle all Flashcards
True or false question that comes in the exam
Vertical curve length must be higher than SSD ( Not true because we have the height of the object that we detect)
We want to find the minimum length of the Crest vetical curve
Vertical curve length must be higher than SSD ( Not true because we have the height of the object that we detect), That is why we compare with the Sight distance
Minimum Crest curve length
Formula is found on slide number 7, We first assume S>L or L
We can use K to find the Minimum length for crest crest crest vertical curves
Formula is on page 11
There is a minimum length of the crest vertical curve
Lmin is 30-100 m or 0.6 *design speed(km/hr) whichever is bigger
For K > 51 ⇒ drainage may be of concern since
the crest curve is rather flat; very important remember it
True
Now we gonna work for the sag vertical curve
In daylight, the sight distance is not restricted
on sag vertical curves
• Critical concern here is with the headlight
sight distance at night, or length of road
illuminated by vehicle’s headlights.
The formula for Sag vertical curve is the following; Also note that we can use K
check page 24 and 25
There is a minimum length of the sag vertical curve
Lmin is 30-100 m or 0.6 *design speed(km/hr) whichever is bigger; it is the same as the crest vertical curve.
Kmax = 51 or else the curve
will be too flat and we will have a drainage problem
True
Example 7 is very important
true
Passing sight distance is only relevant for crest vertical curves because for sag vertical curves, the upcominng car in the opposite direction can always be seen, also at night u can see the headlights for the carcoming
TRue
Minimum curve length to provide for PSD (only for crest remember
The formula is found on page 40, also we can use K as in page 41
The lengths of crest vc’s required to provide
for minimum PSD are substantially longer than
those for SSD
True
Sag vertical curves and overhead structures
Consider sag curves being built under an
overhead structure (mtl tunnel of nahr el kalb)
– Line of sight may be restricted
– Entire curve length may not be visible.