Reading Notes Flashcards
The Grid System
Consist of Equally spaced streets or roads which are perpendicular to each other. This system is often used because of its regularity, simplicity and convenience.
The Radial System
Directs flow to or from a common center, with straight channels of circulation radiating from this center point. A series of by-passes connecting outlying radial can be created, thereby allowing through traffic to skirt the center alleviating congestion.
The Linear System
Connects flow between two points, either along single line or along a series of parallel lines.
The Curvilinear System
Response to the topography of land and aligns with natural contours.
Freeway (Expressway)
Designed to allow movement of large volume of traffic between, around or though urban centers.
Arterial Streets
Continuous vehicular channels that connect to expressways by means of on-off ramps at carefully determined locations. Parking is normally not allowed. Intersections should be separated by at least 800 ft
Collector-Distributor Streets
Serve as the transition between arterial street and the local access streets of neighborhoods. These streets are frequently discontinuous , thereby preventing through traffic.
Local Access Streets
Provide access to low-intensity uses fronting on them. they carry low traffic flows.
Broken-Back Curves
Two curves in the same direction and should be separated by a tangent not less than 200 ft.
Reverse Curves
Two curves in opposite directions and should be separated by a tangent not less than 100 ft.
Compound Curves
Two curves in the same direction with different radii. This should be avoided altogether
Simple Curves
A circular arc connects tangents at each end. may employ tangents of an length.
Acute angle intersection
the intersecting streets are less than 80 -85 degrees should be avoided because it is difficult to negotiate and limits driver visibility.
Cul-de-sac
should not exceed 400 ft. A minimum turnaround at the end of a cul-de-sac should be provided which is at least 80 ft in diameter and free of parking.
Loop Street
Max depth is 700 ft
Block
Max length of a block is 1,600 ft
Curb Radii
Minor street - 12 ft min.
Major street - 50 ft min.
Traffic Signal Required
750 vehicles per hour
Grade Separation required
3,000 vehicles per hour
most common is cloverleaf (based on a system of right turns)
Diamond Intersections
Used when expressways intersect secondary roads
Cartridge Roads
on-site loop distributor and collector drive with carefully located access points to the local road system ( Large Shopping Centers)
Pedestrian movement
a total of 13 sq ft per person is required to move easily without making body contact.
if less than 7 sq ft, pedestrians tend to move as groups rather than individuals.
Primary objectives of good pedestrian circulation
safety, security, convenience, continuity, comfort, and attractiveness.
Wheelchair restrictions
Min turning clear space is 5’
Min passing width for two wheelchairs is 5’
walks should not a gradient greater than 1:20(5%) with a max cross gradient of 1:50 (2%)
Curb Cutouts
Should be identified by a 1/16 inch yellow abrasive anti-slip epoxy finish applied to the entire area of the curb cutout.
Ramps
should not exceed 1:12 (8 1/3%) preferably 1:16 (6 1/4%). Ramps should be min. of 3’ wide and not exceed 30’ in length. Handrail should be located at each side of ramp if rise is greater than 6” or its run I greater than 72”.
Utilities and services
Include: water, gas, electrical, communication systems, wastewater systems, drainage systems, and flood control…
The space beneath the public street right-of-way is the most logical and efficient location.
underground utility location general principles:
- wastewater lines, because of their gravity flow requirements, should have first priority.
- Trunk (main) lines should not be located in major traffic arteries, if possible
- trunk lines for several utilities should not be located in the same street
- the center of streets should be reserved for the wastewater line, unless the street in sufficiently wide to accommodate a dual water system
5’ all utility installations required for the next five years should be installed before a street is paved.
Water main sizes
Often determined by fire protection requirements, are generally 6” in typical residential and 8” in high density districts.
Fire hydrants
urban - 150’
suburban - 600’
Force main
We wastewater is pumped over extensive horizontal distance
Wastewater mains
Lowest structure below street level.
velocities no less than 2.5 feet/second and no more than 10 feet per/second