Design Philosophy Flashcards
what are the 5 characteristics of a safe road
consistent transitions controlled release of info repeated info forgiveness
Design domain can be
thought of as?
a range of values that a design parameter (e.g. coefficient of deceleration,
lane width) might take. These values should be justified in an engineering sense (e.g.
based on test data, sound reasoning, etc) and therefore have a reasonable level of
defence if questioned
what is the operating speed
it is the 85th percentile speed of free speeds of users (not obstructed by other cars)
what is the desired speed
The speed driven at on a long, level tangent when not constrained by other vehicles (depends on drivers perception)
what is the speed environment
assumed value relating to a length of road incorporating several curves . is the 85 percentile value of the desired speed for that length.
what is the design speed
speed chosen based on horizontal/vertical and cross section changes. should not be lower than 85 percentile of operating speed .
what are the four steps in alignment design method
1 estimate speed environment
2 estimate design speed
3 assess speed environmetn
4 if speed environment not as estimated, revise
what is general driver behaviour in regards to speed and curves
will adjust for horizontal curves
will maintain desired speed on grades
how much should the speed vary by and whats the expected speed for the following environments?
-high speed
intermediate
low speed
high speed 100-130 vary
if there is an isolated design feature such as roundabout what must you do to its approach
reduce desgin speed in series of steps or reducing radius curve
