Arterial Design and LOS Analysis

1
Lecture 12

• Arterial Design and LOS Analysis

2
Objectives

• Understand the factors in arterial design
• Understand how arterial LOS is determined

3
Kramers Ten Ideal Arterial Characteristics

• Arterial split of 2/3 to ¾ at all intersections
• Progressive movement in both directions
• Protected left turns used to protect through
  traffic
• Left turn bays provided, with protected phase
• Accommodates large trucks
• Protected pedestrian phases and frequent
  crossings
• Transit operations that does not impede through
  traffic
• Transit stops at locations close to protected
  pedestrian crossings
• Accommodate future growth with minimal effect on
  through traffic
• Variable timing and progression to accommodate
  variable traffic, special events, and emergency
  vehicles

4
Arterial Performance

• Average travel speed of through vehicles
• length arterial or segment length (miles)
• running time per mile total of running time
  per mile on all segments in the arterial or
  section (sec)
• total intersection approach delay totaled
  over all intersections within the arterial or
  section (sec)

5
Signal Spacing

• How can the arterial function be preserved?
• Why is signal spacing is crucial?
• How might signal coordination be better than
  physical improvements?
• What tends to happen to arterial LOS as
  signalized intersections increase?

6
Advanced Planning

• What needs to be considered when planning an
  arterial?
• What are the general planning alternatives?

7
Reallocation of Arterial Space Parking

• How can arterial space be reallocated?

8
Other Aspects of Operation

• What is the overall effect of intersection
  modifications?
• Turn bays (left and right)
• Existence
• Length
• RTOR
• Turn prohibitions
• Arrival patterns
• Signalization

9
Other Aspects of Operation (cont.)

• What is the overall effect of arterial
  modifications?
• Signal spacing
• Parking
• Transit
• Delivery activity
• Land access function
• Special use lanes

10
HCM Procedure for Arterials

• What are the steps to the HCM procedure?
• Establish arterial to be considered
• Determine arterial class and free flow speed
• Define arterial sections
• Compute running time
• Compute intersection approach delay
• Compute average travel speed
• Section
• Facility
• Assess the LOS

11
HCM Procedure for Arterials (cont.)

• What does the procedure do?
• Why are there different arterial classes?
• How are the arterial classes identified?

12
Arterial Speeds

• Free flow speed
• How can running speed be determined?
• How can intersection delay be determined?
• Average travel speed
• What is the correct delay to use in arterial
  evaluation?
• D 1.3d
• Where
• D approach delay (sec/veh)
• d stopped delay for the through movement
  (sec/veh)

13
Arterial vs Intersection Performance

• How are arterial and intersection performance
  related?
• Good arterial performance requires great
  intersection performance
• How can good arterial performance be assured?