Improvements? Not sure exactly what you mean. If you can expand the question a bit, we can give you a better idea about what you're looking for. You might also mean easements or encroachments. Normally I would not think of a pipeline as an improvement---but you might have a pipeline easement. I've never thought of a road as an improvement, but I guess it could be depending on the property (maybe a larger property)
Are you talking about an easement? Here in North Texas where there are a lot of pipelines, these are the most questioned useage. Anything that crosses a property, even if it is aireal (i.e powerlines and such) are ALL called easements on your property.
If that is not what you are seeking, PLEASE try to clarify your question.
I am unconfirmed for your quest of an answer, in many sections of country / states/cities can use different kinds of terms. however what comes to mind are the following words however depends what use for: improvements, developement, redevelopment, real estate development , masterplan communities