conflict points 3-leg intersection 4-leg intersection · pdf file1 chapter 6: intersections...
TRANSCRIPT
1
Chapter 6: Intersections
Conflict Points
4-leg intersection3-leg intersection
9 conflict points 32 conflict points
Intersection Geometry
• Skewed or perpendicular• Corner radius• Turn lanes• Sight distance
2
Skewed Intersection
Skewed Intersection 2
STOP
Corner Radius
3
Traffic Control Types
• No control• YIELD• Stop
– Two-way– All-way (e.g., 4-way)
• Traffic signal• Roundabout
No Control
• Low volume• Good sight
lines
Yield Control
• Low delay • Works well with
good sight lines
4
Stop Control
• Use when approach sight triangle is blocked
• Causes delay• Ineffective at speed control
Two-Way Stop Control
• Intersection of a main road and a side road
• Doesn’t delay main road traffic
All-Way Stop Control
• Intersection of comparable roads– Nearly equal volumes
• Delays all traffic• Guidance in MUTCD
– Entering volume– Crash history– Speed
5
Signals and Roundabouts
• Experienced P.E. should design • Use when traffic volumes are too high
for stop control• More expensive than sign control
Traffic Signals
• High traffic volumes• Work best with light side road traffic• Eight warrants
– One or more should be met• Not a cure-all for safety problems
Roundabouts
• Work well for heavy left turn or crossroad traffic
• Safe and efficient if designed properly• Difficult for pedestrians with poor vision
6
Long Island Roundabout
Intersection Sight Distance
Stopping Sight Distance
7
No Control or Yield
Two-Way Stop
All-Way Stop
8
Signal
Driveways
• Design and spacing affect safety• Permit should be required
Access Management
• Planning of land access• Can reduce congestion and crash rates• If your town is developing, act now!• TRB’s Access Management website
– www.accessmanagement.gov
9
Access Management Example
Intersection Problems
Elementary School
Mai
n St
Schoolhouse Lane
R = 60 feet
Intersection Problem 1
10
YI ELDKa
thy
Lane
3 pines, 15" dia
LAKATHYYI ELD
N
Intersection Problem 2
Intersections
• Intersection geometry• Traffic control• Driveways and access management