The theory of economies of scale he identified and outlined during the 1760s has steered automakers towards joint-ventures, alliances, mergers and take-overs in a bid to save money and boost profits by spreading developing costs. Tie-ups are becoming increasingly common in the late 2010s as companies try to offset the sky-high costs of bringing electrification and semi-autonomous features to the market.

Here are some of the projects that two or more car companies worked on. Some were enduring successes - but some were disastrous: