Why Are American and Arabian Roads the Straightest?

While a winding mountain road offers a driving thrill, the world's longest, perfectly straight roads are found almost exclusively in just a few regions: the American West, the Canadian Prairies, the Middle East, and the Australian outback. This geographic concentration is no accident. It is the direct result of a collision between history, modern engineering, and vast, empty land.

1. The Core Differentiator: When and How Roads Were Built

The fundamental difference between curvy roads (like those often found in Europe) and straight roads (like those in North America and Arabia) is when they were constructed and what they were built around.

Ancient Roots (European Complexity): Many European routes are based on ancient human activity. Roads followed natural features like river systems, ancient Roman military paths (late 300 B.C.), medieval trade routes, and were built to connect pre-established, centuries-old towns and villages. These routes had to constantly curve to avoid existing property and challenging topography.
Modern Simplicity (North America): In contrast, the United States' modern highway system began construction in the 20th century, largely driven by the Federal-Aid Road Act of 1916 and the Federal Highway Act of 1921. Engineers laid these roads across undeveloped, inexpensive, wide-open land where there were few established cities or obstacles to avoid.
Deep Dive: The History of Road Engineering The feasibility of building long, straight routes is thanks to innovations in materials and construction techniques. Learn how engineers like Telford and McAdam revolutionized pavement—from the earliest paved streets in Mesopotamia to the modern use of asphalt—in our dedicated historical guide: Read The History of Road Engineering, from Mesopotamia to Modern Asphalt HERE

2. The Dominance of the Grid System (US & Canada)

For North America, the primary reason for straightness isn't just lack of mountains—it's a legally mandated map.

The sheer, unbending straightness of roads found in the American Midwest and Canadian Prairies is thanks to the Public Land Survey System (PLSS), established in the U.S. by the Land Ordinance of 1785.

This system divided huge tracts of land into a rigid, uniform grid of six-mile square townships . Since land ownership boundaries, property lines, and eventually, county borders were established as perfectly straight lines following this grid, it was immensely cheaper and easier for engineers to lay roads exactly along these straight boundaries.

Example: The straight sections of roads like ND-46 W and US-136 E in the USA, and SK-33 W in Canada, exist because they run precisely along these historical north-south and east-west survey lines.

3. The Desert Factor: Geography, Cost, and Scale (Arabia & Australia)

In desert nations like Saudi Arabia and vast areas of Australia, the lack of obstacles dictates the engineering.

Geographical Simplicity: Vast, flat, arid deserts and salt plains (such as the Nullarbor Plain traversed by the Eyre Highway) have virtually no geological features (mountains, major rivers, or forests) to force a curve.
Engineering Logic: When the objective is to connect two distant points (A to B) across undeveloped terrain, the shortest, most cost-effective path is always a straight line. Every unnecessary curve requires more material, more labor, and more cost.
The Ultimate Example: This logic produced the world's straightest road: Highway 85 in Saudi Arabia, which spans an incredible 822 km (510 mi) of uninterrupted straightness across the flat desert between Arar and Al Nairyah, as well as the famous Highway 10.

Conclusion: The Formula for Straightness

The world's longest straight roads are born when three specific factors align:

Empty Space: Vast, undeveloped, or topographically simple land (deserts, plains).
Modern Timing: Constructed post-1900, free from the constraints of ancient settlements.
Geometric Intent: Built along strict, straight survey lines (US/Canada) or following the path of least resistance for cost efficiency (Arabia/Australia).