Well, as far as I am concerned, I give negative impedance (like -1 seconds) against Reverse turn, if I do not want Reverse turns. That restricts Reverse turn.
In Network Dataset, under Attribute tab, when you add an attribute, there is an option to make an attribute "Use by default". You have to check the check box located at the Add Attribute dialog box, so that the attribute acts by default. Generally, the time-related cost attribute like Minutes, (also Oneway, Hierarchy) are made to be used by default; while length related cost-attribute like Meters, Length, Miles, etc are not made to be used by default. Whether an attribute is being used by default or not, you will be able to know by seeing a small blue-coloured D mark against that attribute. Under such circumstances, the shortest route will be calculated based on time-related cost attribute.
Koushik Paul
India