Movement and Utilities Flashcards
Which vehicular circulation system generates the most visually chaotic effect?
Linear
4 basic categories of traffic arteries
- Freeways
- Highways (arterial streets)
- Collector-distributor streets
- Local access streets
Which type of street usually doesn’t allow parking, is 2-3 lanes wide, and generally has a speed limit of 35mph?
Arterial streets – highways
Why are collector-distributor streets often discontinuous?
To prevent through-traffic and reduce speeds
What is the top of the road called?
The crown
What is the transverse slope of a street?
Between 1/8” and 1/2” per foot
How wide are traffic lanes on major roads?
11-12 ft
What are minimum widths of landscape strips at the roadside?
7’ min. with trees, 4’ min. with ground cover only
What is a tangent?
Straight section of the middle of the road which may or may not be level
4 rules of thumb for laying out a road
- Two curves in the same direction (broken back) should be separated by a tangent at least 200 ft long
- Two opposing curves (reverse) should be separated by 100 ft
- Two curves in the same direction with different radii should be avoided
- Simple curves may have tangents of any length
Vertical curving road alignment involves _____ curves rather than circular
Parabolic (flattened)
Intersections on a major arterial roadway should be separated by at lease _____
800 ft
Overall length of a cul-de-sac must be no more than ___ with a minimum turnaround radius of __.
400 ft… 80 ft
Max length of a block
1,600 ft
Min curb radii on minor intersections versus major street
12 ft versus 50 ft
What is the max # of cars per hour before you need a stoplight?
750
What is the max # of cars before you need a grade separation?
3,000
Most common grade separation intersection
Cloverleaf – simple, based on right turns
What is the advantage of a direct left-turn interchange?
More complex and expensive but allows more lanes to operate at high speed in all changes of direction
When do you use diamond intersections? Advantages?
Where expressways intersect secondary roads … They are simple and cheap, using little space
Slope of on ramps vs off ramps
Up ramps: bt 3-6 %
Down ramps: 8%
Which vehicular circulation network produces the most efficient use of land… With what one helpful side effect?
Linear system… But it also generates a large amount of commercial “incubator” (new business) space
What is a reasonable minimum width for a typical parking stall?
8’-4” (20” clearance bt full size cars)