How to Create a Road Network

Map of Ikeja in Lagos State Using ArcGIS Pro and OpenStreetMap Data

Mapping a city’s road network is a critical step toward understanding its connectivity, transportation challenges, and accessibility. Lagos State, one of Africa’s largest and busiest urban regions has a complex road network that can be visualized and analyzed using GIS tools and open-source data.

In this blog post, we’ll walk you through what a road network map is, why it’s important, what data is needed to create one, and how to build it using ArcGIS Pro and OpenStreetMap data.

What is a Road Network Map?

A road network map is a visual representation of a region’s road infrastructure including major roads, highways, local streets, and their connections. It doesn’t just show roads as lines on a map, it reflects how those roads connect and how accessible different parts of a city are through the transportation network.

Why is a Road Network Map Important?

Road network maps are valuable for many reasons:

• Urban Planning: Help planners identify road gaps and plan new routes.
• Emergency Services: Improve response times by analyzing the fastest routes.
• Logistics & Transportation: Optimize delivery routes and reduce traffic bottlenecks.
• Public Services: Determine how accessible public facilities like hospitals and schools are.
• Research: Analyze traffic flow, commuting patterns, or urban expansion.

For Lagos, a city with constant traffic and rapid urban growth, a road network map helps to visualize and tackle these issues with data driven decisions.

Data You Need to Create a Road Network Map

To build a road network map of Ikeja in Lagos State, you’ll need the following:

• Road Network Data: You can get detailed, up-to-date road data from OpenStreetMap (OSM). It includes all road types such as highways, expressways, residential roads, service roads, and more.

• Administrative Boundary: This helps you clip or limit your road data to Ikeja in Lagos State alone. You can download it from platforms like: GADM, DIVA-GIS e.t.c

• GIS Software: You’ll need ArcGIS Pro (a professional GIS application by Esri) to process, clean, and visualize the data.

How to Create a Road Network Map of Ikeja in Lagos State using ArcGIS Pro

Step 1: Download Road Data from OpenStreetMap

1. Go to Geofabrik Downloads.
2. Download the Nigeria extract (usually a .osm.pbf file).

Step 2: Load OSM Data into ArcGIS Pro

1. Open ArcGIS Pro and create a new project.

2. Add my Nigeria LGA boundary data

Step 3: Clip Roads to Ikeja LGA in LGA Boundary Data

1. Extract my Ikeja local government in LGA boundary shapefile as a layer in your project.

                    Select by attribute > select Ikeja > export layer

2. Add my OSM road data and use the Clip tool (Analysis > Tools > Clip) to extract only roads that fall within Ikeja, Lagos.

Step 4: Symbolize and Classify Roads

1. In the Symbology pane, classify roads by type or highway attribute (e.g., motorway, trunk, primary, residential).
2. Use different colors or line widths for each category:
   • Tertiary roads: thick black
   • Primary roads: green
   • Secondary roads: dotted black

Step 5: Add Map Elements (Legend, Title, North Arrow)

1. Go to Insert > Legend, North Arrow, and Scale Bar.
2. Add a descriptive Title, e.g., “Road Network Map of Ikeja”
3. Use the Layout View to design your map for printing or exporting.

Creating a road network map of Ikeja in Lagos State using OpenStreetMap and ArcGIS Pro is a powerful way to understand the city’s connectivity. This workflow gives you a strong foundation to analyze and visualize road systems.