rerouted because their original routes became impassable experienced an export growth rate 33.7 percent lower than their unaffected counterparts.

Ali et al (2015) in their study of the Democratic Republic of Congo show that higher transportation costs have a significantly negative impact on wealth and a significantly positive impact on the probability of being multi-dimensionally poor in conflict-affected areas. The location of conflict is also important in determining its effect. Conflict near households has a strongly negative impact on a household’s wealth, and conflict near markets has a large, positive impact on the probability of being multi-dimensionally poor. In areas of the Democratic Republic of Congo with low or no conflict, investment in decreasing transportation cost emerges as a highly effective way of generating economic growth, as long as parallel measures are taken to enhance security.

Turning to the papers on the relationship between transport infrastructure and environmental conflicts, road improvement planning in tropical forest regions is unlikely to maximize welfare unless it anticipates and incorporates negative environmental impacts. Damania and Wheeler (2015) estimate an econometric model of deforestation that incorporates the economics of road improvement. The authors find large, highly significant effects of upgrading on the intensity and extent of forest clearing along road corridors. The results highlight how proprietors’ decisions to clear forest are highly sensitive to market access, land opportunity values, official protection status, and topography. The paper also estimates the impact of violent conflict on deforestation in Sub-Saharan Africa, predicting a 10-20 percent increase in deforestation as a result of conflict, though varying widely according to prior road conditions and characteristics of local economies. In addition, many corridors lead to significant extensions in the outer margin of forest clearing.

**Table 12: Survey of selected papers on the development impact of national highways in Africa and Latin America**

|**Author**|**Level of**<br>**Analysis**|**Country/**<br>**Region**|**Indicator of**<br>**Development**|**Main Findings**|
|---|---|---|---|---|
|Buys et al<br>(2010) *|Inter-city|Sub-Saharan<br>Africa|Trade, Jobs|Continental network upgrade would expand intra-African trade by<br>$250 bn over 15 years, while creating jobs and benefiting rural poor.|
|Bosede et al<br>(2013) *|Locality|Nigeria|Income|Transport investment in national highways can make a significant<br>positive contribution to growth.|
|Morten and<br>Oliveira (2018)|Locality|Brazil|Trade,<br>Migration|Road improvement increased welfare by 13%, mainly due to a 28%<br>reduction in trade costs, which could increase with more migration.|
|Martincus and<br>Blyde (2013) *+|Firm|Chile|Trade|Firms with export routes disrupted by an earthquake, saw 33% lower<br>export growth, indicating an export to distance elasticity of -1.42.|
|Ali et al (2015)+|Household|Congo,<br>Dem. Rep.|Wealth,<br>Poverty|High transport costs have a significant negative impact on wealth and<br>a significant positive impact on poverty, particularly in conflict areas.|

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