Background: There are great disparities in the quantity and quality of infrastructure.
European countries such as Denmark, Germany, Switzerland, and the UK have close
to 200 km of road per 100 km2, and the Netherlands over 300 km per 100 km2. By
contrast, Kenya and Indonesia have <30, Laos and Morocco <20, Tanzania and
Bolivia <10, and Mauritania only 1 km per 100 km2. As these figures show, there is a
significant backlog of transport infrastructure investment in both rural and urban
areas, especially in sub‐Saharan Africa. This situation is often exacerbated by weak
governance and an inadequate regulatory framework with poor enforcement which
lead to high costs and defective construction.
The wellbeing of many poor people is constrained by lack of transport, which is
called “transport poverty”. Lucas et al. suggest that up to 90% of the world's population
are transport poor when defined as meeting at least one of the following
criteria: (1) lack of available suitable transport, (2) lack of transport to necessary
destinations, (3) cost of necessary transport puts household below the income
poverty line, (4) excessive travel time, or (5) unsafe or unhealthy travel conditions.
Objectives: The aim of this evidence and gap map (EGM) is to identify, map, and
describe existing evidence from studies reporting the quantitative effects of transport
sector interventions related to all means of transport (roads, rail, trams and
monorail, ports, shipping, and inland waterways, and air transport).
Methods: The intervention framework of this EGM reframes Berg et al's three categories
(infrastructure, prices, and regulations) broadly as infrastructure, incentives,
and institutions as subcategories for each intervention category which are each
mode of transport (road, rail trams and monorail, ports, shipping, and inlands waterways,
and air transport). This EGM identifies the area where intervention studies
have been conducted as well as the current gaps in the evidence base.This EGM includes ongoing and completed impact evaluations and systematic reviews
(SRs) of the effectiveness of transport sector interventions. This is a map of
effectiveness studies (impact evaluations). The impact evaluations include experimental
designs, nonexperimental designs, and regression designs. We have not included
the before versus after studies and qualitative studies in this map. The search
strategies included both academic and grey literature search on organisational
websites, bibliographic searches and hand search of journals.
An EGM is a table or matrix which provides a visual presentation of the evidence in a
particular sector or a subsector. The map is presented as a matrix in which rows are
intervention categories (e.g., roads) and subcategories (e.g., infrastructure) and the
column outcome domains (e.g., environment) and subcategories as (e.g., air quality).
Each cell contains studies of the corresponding intervention for the relevant outcome,
with links to the available studies. Included studies were coded according to
the intervention and outcomes assessed and additional filters as region, population,
and study design. Critical appraisal of included SR was done using A Measurement
Tool to Assess Systematic Reviews (AMSTAR ‐2) rating scale.
Selection Criteria: The search included both academic and grey literature available
online. We included impact evaluations and SRs that assessed the effectiveness of
transport sector interventions in low‐ and middle‐income countries.
Results: This EGM on the transport sector includes 466 studies from low‐ and middleincome
countries, of which 34 are SRs and 432 impact evaluations. There are many
studies of the effects of roads intervention in all three subcategories—infrastructure,
incentives, and institutions, with the most studies in the infrastructure subcategories.
There are no or fewer studies on the interventions category ports, shipping, and waterways
and for civil aviation (Air Transport).
In the outcomes, the evidence is most concentrated on transport infrastructure,
services, and use, with the greatest concentration of evidence on transport time and
cost (193 studies) and transport modality (160 studies). There is also a concentration
of evidence on economic development and health and education outcomes. There
are 139 studies on economic development, 90 studies on household income and
poverty, and 101 studies on health outcomes.
The major gaps in evidence are from all sectors except roads in the intervention. And
there is a lack of evidence on outcome categories such as cultural heritage and
cultural diversity and very little evidence on displacement (three studies), noise
pollution (four studies), and transport equity (2). There is a moderate amount of
evidence on infrastructure quantity (32 studies), location, land use and prices (49
studies), market access (29 studies), access to education facilities (23 studies), air
quality (50 studies), and cost analysis including ex post CBA (21 studies).
The evidence is mostly fromEast Asia and the Pacific Region (223 studies (40%), then the
evidence is from the sub‐Saharan Africa (108 studies), South Asia (96 studies), Latin
America & Caribbean (79 studies). The least evidence is from Middle East & North Africa
(30 studies) and Europe & Central Asia (20 studies). The most used study design is other
regression design in all regions, with largest number from East Asia and Pacific (274).
There is total 33 completed SRs identified and one ongoing, around 85% of the SR are
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rated low confidence, and 12% rated as medium confidence. Only one review was rated
as high confidence. This EGM contains the available evidence in English.
Conclusion: This map shows the available evidence and gaps on the effectiveness of
transport sector intervention in low‐ and middle‐income countries. The evidence is highly
concentrated on the outcome of transport infrastructure (especially roads), service, and
use (351 studies). It is also concentrated in a specific region—East Asia and Pacific (223
studies)—and more urban populations (261 studies). Sectors with great development
potential, such as waterways, are under‐examined reflecting also under‐investment.
The available evidence can guide the policymakers, and government‐related to
transport sector intervention and its effects on many outcomes across sectors.
There is a need to conduct experimental studies and quality SRs in this area. Environment,
gender equity, culture, and education in low‐ and middle‐income countries
are under‐researched areas in the transport sector.