1. *vengDaq taw vIghoS* would be however (without further context) ambiguous, right? It could mean: *I go along the road toward the city* or *I go along the road in the city*.

This is not ambiguous in Klingon. -Daq simply has a larger scope of meaning than the various English prepositions that it corresponds to. This is true of any use of the locative. yuQDaq jIHtaH. This could mean I am on the planet, and this is the translation one would commonly expect, but it could also mean I am in the planet or by the planet. In fact, it means all of those at once; it means I am locative-planet.

4. How can I distinguish between *I go along the road* and *I approach toward the road*? Following SuStel's explanation, and supposing I've understood it right, I would say *taw vIghoS* could only mean *I go along the road*, *tawDaq vIghoS* would have two meanings: *I go along the road* with a redundant *-Daq* or *I go along (something) toward the road* with an elided pronoun. But with De'vID's explanation I'm not sure any more.

Using ghoS? It will always be ambiguous without further context. taw vIghoS can mean I go along the road, but it could also mean I go to the road, where the road is simply the name of the destination, outlining your course to the road. It's not about whether or not you use -Daq. Instead of the course being the road's length, the course is that course which leads to the road.

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SuStel
http://trimboli.name