Learn Spanish (Latin America): Aseguraron que ampliarían la vía pronto. - They assured that they would expand the road soon.

Asegurar means to declare or state a fact (to assure or claim). Because it expresses certainty or a declaration rather than doubt, emotion, or a command, it takes the indicative mood. The conditional ampliarían (would expand) is used here because it describes a future action from the perspective of the past.

How does the meaning change if I use the imperfect ampliaban instead of ampliarían?

The conditional ampliarían means they would expand it, showing that the expansion was planned for the future at the time they spoke. If you said ampliaban, it would mean they were expanding it, implying the roadwork was already happening at the exact same time they made the announcement.

What exactly is la vía? Is it different from la calle or la carretera?

La vía is a broad term for a route, track, or road. In the context of urban planning or traffic, it often refers to an important thoroughfare or artery. Calle usually refers to a regular city street, while carretera specifically means a highway. La vía sounds a bit more official or technical, which fits perfectly with an announcement about public works.

Can asegurar also mean to buy insurance for something?