a divided (two-way) highway has grass or something between the going and coming lanes...a two-way road has no divider between the lanes.

A divided highway may have 2, 4, 6, or even 8 lanes.

Two way roads can also have multiple lanes, but no dividers.

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Note added at 17 hrs (2016-02-05 15:54:46 GMT)
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I did an informal Google check and both are used. However, I think that since most divided roads are highways, we hear that more often.

Also, note that the British use a lot of different vocabulary for transportation terms...the American divided highway is "dual carriageway" in the UK