Sprawl happens when there is available undeveloped land. Roads are just a symptom.
People build outwards first and then upwards.
People build outwards first and then upwards.
We have more than a century of data showing that roads are subject to induced demand. If you build more roads, people move and sprawl (and take more trips in general) until traffic is once again unbearably bad.
If you build more lanes, more people move further out. Roads create sprawl.