Feeder Road Prioritization Engineering Issues G2a Cost Estimation Survey G2b Road Condition Survey J

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Feeder Road PrioritizationEngineering
IssuesG2a Cost Estimation SurveyG2b Road
Condition SurveyJohn Hine / Simon Done

• November 2000

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G2a G2bCost Estimation Survey Road
Condition Survey

• Access Roughness
• Access Category A Traffickability
• Access Category B Passability
• Access Category C Roughness Key
• Spot Improvements Traffickability Key
• Full Rehabilitation Passability Key
• Problems with Spot Impments Effects of
  impments
• Cost Est. Survey vs. MPBS Survey Procedure
• Survey Procedure
• Consistency is required
• Typical Results
• Accessibility Strip Map
• Calculation of catchment areas

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Cost Estimation Survey

• Access
• The priority is on arriving at the destination
  rather than doing so quickly or smoothly.
• Access permits maximum benefit at minimum cost.
• Access should be reliable if farmers are to plant
  surplus crops and traders are to buy and operate
  vehicles.
• Access is more appropriate for short roads (20
  km?) than for long roads (100 km?), and for low
  traffic than high traffic.
• Access should be provided for all vehicle types
  that may use the road.
• Access should be year round (rather than
  seasonal), except perhaps for closures of up to a
  day or two.
• The biggest threat to access is rainfall and
  runoff.

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Cost Estimation Survey

• Access Category A
• Sites where, for local vehicle types
• Year round access is impossible even if in an
  emergency
• Road users are in danger of injury
• The road is under water for time periods of more
  than two consecutive days
• Improvement of Category A sites will provide
  emergency access in the short term

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Cost Estimation Survey

• Access Category B
• Sites where, for local vehicle types
• Year round access is possible, but unreliable
• Access is likely to be lost in the near future
• Road condition is likely to deteriorate as each
  vehicle passes
• Road condition is likely to deteriorate as each
  rainstorm passes
• The road is badly eroded
• Motor vehicle speed is reduced to below normal
  walking speed
• Cyclists are forced to dismount
• Vehicles are liable to damage as they pass
• Improvement of Category A B sites, with
  maintenance, will provide reliable year round
  access in the long term. This level of
  improvement may be termed spot improvements.

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Cost Estimation Survey

• Access Category C
• Sites where, for local vehicle types
• Year round access is possible, and reliable
• Road condition is stable
• Deterioration is unlikely in the near future
  under existing conditions
• Surface roughness is not enough to slow motor
  vehicles to below walking speed
• Improvement of Category A, B C sites will
  maintain access and permit smooth, comfortable
  travel. This level of improvement may be termed
  full rehabilitation

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Cost Estimation Survey

• Spot (Accessibility) improvements
• This refers to the improvement of localised sites
  where access is
• lost,
• unreliable,
• at risk in the near future, or
• dangerous,
• but leaving those lengths of road where vehicles
  can pass safely and reliably all year round.
• The appearance of the road may be variable, but
  the quality of work carried out is high, and the
  work should be robust.
• Spot improvements may be appropriate for the
  involvement of local communities.

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Cost Estimation Survey

• Full rehabilitation
• This refers to the improvement of the entire road
  such that access is safe and reliable all year
  round, and also that a smooth, often gravelled,
  surface permits comfortable travel along the
  whole length

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Cost Estimation Survey

• Problems with Spot improvements
• Can be unacceptable to
• Politicians
• Road Authorities
• Travelling public
• Tax paying electorate
• Road contractors
• But
• A cost effective way of providing access to many
  people at minimum cost.

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Cost Estimation Survey

• Cost Estimation Survey MPBS
• One-off improvement cost Repeated maintenance
  cost
• Makes a road maintainable Keeps a road
  maintainable
• Fast and approximate Detailed and accurate
• Used for Prioritization Used for letting
  contracts
• Estimates required activities Schedules actual
  activities
• Condition allocated to sections Condition
  allocated to road
• All possible improvement works Only periodic and
  routine mt
• Groups activities together Keeps activities
  separate
• Simplifies to 17 activities Requires 34 separate
  activities
• Unit costs are approximate Unit costs are exact
• Spot imp. rehabilitation costs Rehabilitation
  cost only
• Limited decision flexibility Great decision
  flexibility

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Cost Estimation Survey

• Survey Procedure
• Survey during the rains if possible
• Divide the entire road into sections
• Identify the problem type for each section
• Identify the vehicle types likely to use the road
• Record the Access Category of each section
• Estimate required quantities to treat the problem
• Transfer the unit cost for each treatment
• Calculate the total cost for each Access Category
• Calculate the costs of emergency access, spot
  improvements and full rehabilitation
• Incorporate costs into the Prioritization
  procedure

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Cost Estimation Survey

• Consistency is required during survey
• Dividing a road into sections
• Recording the Access Category
• Recording the Problem Type
• Estimating required quantities

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Cost Estimation Survey

• Typical results - a road of 5.26 km
• Full rehabilitation (Cat ABC)
• 52,081 100
• Spot Improvements (Cat AB)
• 15,909 30
• Emergency Access (Cat A)
• 4,067 8

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Cost Estimation Survey

• Accessibility Strip Map
• Used to record
• junctions
• sites where access is lost
• sites where access is difficult
• In order to assess the social impact of
• existing road condition
• expected road condition
• On the affected population

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Cost Estimation Survey

• Calculation of catchment areas
• Identify all water crossings - GPS, landmarks,
  etc
• Locate the crossing on map - 150,000
• Measure catchment size
• Use catchment size to estimate cost of structure

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Road Condition Survey

• Roughness Definition
• This refers to the surface condition of the road.
  Definitions of four roughness levels are
  suggested, and it is possible to correlate each
  level to an IRI value, or the comfortable travel
  speed of a vehicle, although the latter requires
  careful calibration.
• Roughness is recorded by
• Direct assessment of IRI
• Correlation with description - good gravel,
  average, poor, extremely poor
• Roughness Key - based on correlation with
  comfortable travel speed

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Road Condition Survey

• Traffickability Definition
• This refers to factors that significantly reduce
  traffic volumes (but do not absolutely prevent
  movement) such as poor road condition in the wet
  season or, on occasion, extreme roughness. E.g.
  a road may be said to have traffickability
  problems if, at some point in the year, the wet
  season traffic is less than 50 of the dry season
  traffic.
• Traffickability is recorded by
• Assessment of length and duration of
  traffickability problems
• Traffickability Key - based on correlation with
  the proportion of the road of Category A or B

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Road Condition Survey

• Passability Definition
• This refers to the inability of vehicles to
  travel along the road on grounds of poor road
  condition. A road is said to have passability
  problems if, for a period of at least two days at
  some point in the year, a vehicle which would
  normally use the road is unable to pass.
• Passability is recorded by
• Assessment of duration of passability problems
• Passability Key - based on correlation with the
  Cat. A water crossing of greatest cross section
• (or length of carriageway of Cat. A)

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Road Condition Survey

• Roughness Key
• This refers to the surface condition of the road.
  Definitions of four roughness levels are
  suggested, and it is possible to correlate each
  level to an IRI value, or the comfortable travel
  speed of a vehicle, although the latter requires
  careful calibration.
• Description IRI Speed (kph)
• G Good gravel 6 gt 60
• A Average 9 40 60
• P Poor 12 20 40
• E Extremely poor 17 lt 20

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Road Condition Survey

• Traffickability Key
• The Traffickability Key is based on the
  assumption that a single, isolated, difficult
  site will not in itself cause traffic levels to
  drop, but that as the total length of road where
  access is difficult increases, more traffic will
  be dissuaded from travelling and the duration of
  problems will extend. Thus the percentage of the
  road length which is of Category A or B is used
  to estimate the duration of the problems.
• L(AB) / Ltotal () Duration of traffickability
  problems (months)
• 0 10 0
• 10 30 0.25 x Rainy season
• 30 50 0.50 x Rainy season
• gt 50 0.75 x Rainy season

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Road Condition Survey

• Passability Key
• The Passability Key is based on the assumption
  that closure of a road depends on a single site,
  rather than an accumulation of sites in the
  Traffickability Key. Only Category A sites are
  considered, since the definition of this Category
  is the loss of access.
• Sites of Category A Duration of passability
• Channel XS Area problems (months)
• 0 1 m2 0.25 x Rainy season
• 1 3 0.50 x Rainy
• 3 10 0.75 x Rainy
• gt 10 1.0 x Rainy season
• Any rain related carriageway
• problem of Cat. A 0.50 x Rainy season

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Road Condition Survey

• Effects of improvements on Road Condition
• The improvement works have the following effect
  upon
• Improvements are
• made to sites of
• Access Category Roughness Traffickability Passabi
  lity
• Category A ? ? ?
• Remains rough Problems remain Problems remain
• Category A B ? ? ?
• (spot improvements) Remains rough, Problems
  solved Problems solved
• but may reduce
• somewhat
• Category A, B C ? ? ?
• (full rehabilitation) Smooth Problems solved
  Problems solved

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Road Condition Survey

• Survey Procedure
• Assess existing overall roughness, passability
  and traffickability of the road - by interview,
  direct observation, or using Keys
• Assess expected overall roughness, passability
  and traffickability after the road has been
  improved to a Spot Improvement or a fully
  rehabilitated standard. Guidance is provided for
  this assessment
• Incorporate existing and expected conditions into
  the Prioritization Index