Appendix A: Sources and Details of Impact Response Values

Road Impact and Costing Information

Paved Road Impact and Costing Guidelines

Paved Roads
Impact and/or Action Description / Paved Roads
Technical Description of Maintenance and Impact / Primary
Paved Road
Cost per KM / Secondary Paved Road
Cost per KM / Tertiary
Paved Road
Cost per KM
Baseline Costs / Full Rehabilitation (20 years) / Re-paving; any necessary re-grading / $500,000 / $150,000 / $90,000
Annual Maintenance / Patching of cracks and potholes / $15,000 / $7,500 / $2,700
International Adjustment Factor / Ranges from 97%-102% of baseline US costs, country-specific
Standards Used for Estimate / US DOT modified for World Bank International construction guidelines
Adaptation Option and Cost / Adapt, Temperature Increase / Change asphalt binder to meet appropriate temperature guidelines / Cost of binder upgrade plus increase in annual maintenance costs attributed to temperature impacts
Adapt, Temperature Decrease / N/A
Adapt, Precipitation Increase / Increase drainage capacity through increase in base layer / Increase in annual maintenance costs for precipitation
Adapt, Precipitation Decrease / N/A
Adapt, Extreme Event Increase in Frequency or Severity / Increase size of culverts and enhance drainage through increase base / Cost estimated based per-km density of drainage infrastructure ; cost of increased base
No Adapt Options and Cost / No Adapt, Temperature Increase / Increase in cracking and rutting / Associated annual maintenance costs
No Adapt, Temperature Decrease / N/A
No Adapt, Precipitation Increase / Increase in wear and cracking / Associated annual maintenance costs and increased cost of reduced lifespan
No Adapt, Precipitation Decrease / N/A
No Adapt, Extreme Event Increase in Frequency or Severity / Sub-base erosion compromises surface integrity and reduces lifespan / Associated annual maintenance costs and increased cost of reduced lifespan

Source: International Road Federation, COWI, FHWA DOT

Gravel Road Impact and Costing Guidelines

Gravel Roads
Impact and/or Action Description / Gravel Roads
Technical Description of Maintenance and Impact / Primary
Gravel Road
Cost per KM / Secondary Gravel Road
Cost per KM / Tertiary
Gravel Road
Cost per KM

Baseline Costs / Initial Construction / Create gravel road to technical standards based on climate and traffic projections / $225,000 / $135,000 / $75,000
Full Rehabilitation (10 years) / Replenish gravel top layer and re-grade surface / $225,000 / $90,000 / $45,000
Annual Maintenance / Replenish gravel where required / $4,200 / $3,000 / $1,500
International Adjustment Factor / Ranges from 97%-102% of baseline US costs, country-specific
Standards Used for Estimate / US DOT modified for World Bank International construction guidelines
Adaptation Option and Cost / Adapt, Temperature Increase / N/A
Adapt, Temperature Decrease / N/A
Adapt, Precipitation Increase / Increase sub-base for drainage, infrastructure when necessary / Increase in annual maintenance costs for precipitation, increase in construction cost when necessary and road is rehabilitated
Adapt, Precipitation Decrease / N/A
Adapt, Extreme Event Increase in Frequency or Severity / Increase size of culverts and enhance drainage through increase base / Cost estimated based per-km density of drainage infrastructure ; cost of increased base
No Adapt Options and Cost / No Adapt, Temperature Increase / N/A / Associated annual maintenance costs
No Adapt, Temperature Decrease / N/A
No Adapt, Precipitation Increase / Reduced lifespan for gravel surface / Associated annual maintenance costs and increased cost of reduced lifespan
No Adapt, Precipitation Decrease / N/A
No Adapt, Extreme Event Increase in Frequency or Severity / Increased erosion of top layer, potential washout of sections of road / Associated annual maintenance costs and increased cost of reduced lifespan

Source: International Road Federation, COWI, FHWA DOT

Unpaved Road Impact and Costing Guidelines

Unpaved Roads
Impact and/or Action Description / Unpaved Roads
Technical Description of Maintenance and Impact / Secondary
Unpaved Road
Cost per KM / Tertiary Unpaved Road
Cost per KM
Baseline Costs / Full Rehabilitation (5 years) / Replenish dirt; any necessary re-grade surface / $50,000 / $25,000
Annual Maintenance / Re-grading and filling where necessary / $1,200 / $750
International Adjustment Factor / Ranges from 97%-102% of baseline US costs, country-specific
Standards Used for Estimate / US DOT modified for World Bank International construction guidelines
Adaptation Option and Cost / Adapt, Temperature Increase / N/A
Adapt, Temperature Decrease / N/A
Adapt, Precipitation Increase / Upgrade to appropriate gravel road given traffic and climate projections / Cost of new gravel road construction, savings in maintenance for unpaved road
Adapt, Precipitation Decrease / N/A
Adapt, Extreme Event Increase in Frequency or Severity / Upgrade to appropriate gravel road given climate projections / Cost of new gravel road construction, savings in maintenance for unpaved road
No Adapt Options and Cost / No Adapt, Temperature Increase / N/A
No Adapt, Temperature Decrease / N/A
No Adapt, Precipitation Increase / Increase in rutting and potholes, increase erosion of surface layer / Associated annual maintenance costs and increased cost of reduced lifespan
No Adapt, Precipitation Decrease / N/A
No Adapt, Extreme Event Increase in Frequency or Severity / Increased erosion of top layer, potential wash out of sections of road requiring extensive rehabilitation / Associated annual maintenance costs and increased cost of reduced lifespan

Source: International Road Federation, COWI, FHWA DOT