A Roughness

1
RCA Forum

• A Roughness Geometry Based Truck Ride
  Indicator
• Mark Owen Transit New Zealand

2
Presentation Outline

• Part 1 Development of Transits TRI
• Part 2 Application to State Highway Management

3
Development of TRI

• Why the emphasis on truck ride?
• Criteria for determining and prioritising
  candidate sites for truck ride improvement.

4
Problem Identified

• Truck drivers less satisfied with State Highways
  than other users.
• Dissatisfaction publicised through NZ Truckings
  Worst Roads Quest.
• Feature item on TV Current Affairs show.
• Face to face interviews with 300 truck drivers.
• Road undulations highly important issue requiring
  attention.

5
Limitation of NAASRA Roughness

• Reflects roughness observed by occupants of short
  wheelbase cars.
• Highlights roughness caused by localised
  disturbances.
• Pitch and roll modes of trucks excited by road
  irregularities that are spaced between 5.5m and
  17m.
• Can be brought about by heave or subsidence of
  subgrade.

6
Criteria for Truck Ride Improvement

• Criterion 1 (Roughness Related)
• Two conditions must be satisfied
• 100 m lane roughness ? 4 IRI m/km (i.e. 105
  NAASRA counts/km).
• A difference of 5 IRI (I.e. 130 NAASRA counts/km)
  or greater between the maximum and minimum 20 m
  wheel path IRI roughness values within the 100 m
  length.

7
Criteria for Truck Ride Improvement

• Criterion 1 is Transits Truck Ride Indicator
  (TRI).
• 1 of SH network, corresponding to 213 lane-kms,
  satisfies the two conditions of the interim TRI.

8
Criteria for Truck Ride Improvement

• Criterion 2 (Length Related)
• TRI conditions satisfied over 2 or more 100m
  adjacent lengths.
• Criterion 3 (Traffic Related)
• HCV traffic ? 100 v/l/d

9
Criteria for Truck Ride Improvement

• Criterion 4 (Truck Rotational Response)
• Resultant pitch and roll response (TRR)
• ? 4.25 deg/s

10
Measured Response for SH 4
11
Comparison of Measured and Predicted Ride Quality

• R2 0.95, Standard Error 0.25 deg/s

12
Test Truck
13
Truck Instrumentation
14
Ongoing Developments

• Refinement of Selection Criteria for Truck Ride
  Improvement Sites
• Roughness/IRI
• Lane IRI
• Crossfall
• Speed
• Gradient

15
Application to State Highways

• Truck Ride Improvement
• new item funded as Pavement Smoothing
• Expenditure to date
• 2000/01 3.1M 37km
• 2001/02 3.7M 24km
• 2002/03 2.3M 29km
• Total expenditure 9M (to date)

16
Procedure Adopted

• RAMM SH database analysed.
• Top sites for each TNZ region.
• Sites inspection to confirm appropriateness.
• Road Transport Associations canvassed.
• Smoothing works costed.
• B/C analysis performed.
• Projects with BCR 4 funded.
• Transit staff also rode in trucks to experience
  problems first hand.

17
Inputs Required for B/C Analysis

• Structural Number (either FWD or Benkelman Beam
  based) or roughness progression over a number of
  years.
• Existing lane roughness.
• Existing HCV traffic (v/l/d) plus projected
  growth.
• Average HCV speed.
• Cost of smoothing works.

18
Example Truck Ride Site ( SH2 RS243 RP3.2- 4.2 )
19
Example Truck Ride Site ( SH57 Tielcey Park )
20
Example Truck Ride Site ( SH56 RP 0/4.3-4.9 )
21
Characteristics of Truck Ride Improvement Sites

• Settlement
• Slope instability/ground movement
• Peat/Swampy subgrade
• Bridge decks e.g hogging
• Poor road geometry
• Rock/roll
• Warp rates (corners)
• Corrugations

22
Typical Repairs

• Grader laid asphaltic concrete.
• Granular overlay.
• Stabilised overlay.
• Typically, less than 100,000 lane-km to achieve
  complying B/C.

23
Successes

• Proactive identification of sites
• Trucking concerns being addressed
• SH network smoothness is being improved
• Positive feedback from local RTAs
• Silver ACENZ award
• Plus other Market Research awards

24
Summary

• An innovation focussed on road user requirements
• Ability to respond to trucking needs
• Low cost tool widespread, effective solution
• Continued road user consultation
• Improving SH network ride/comfort