I'm working on an application to route oversize vehicles. I've built the network dataset from the Navteq data and have applied a number of restrictions to route oversize vehicles. One remaining issue has to do with mast arm features which affect travel in only one direction on a bi-directional road. Mast arms typically extend over only part of a road: i.e. an overheight truck would not be able to pass going northbound, but southbound is OK because the mast arm only extends over the northbound side of the road. Applying a network height parameter on that segment causes the route solver to avoid that segment regardless of direction of travel. I would like to be able to allow southbound travel, but not northbound. The feature class represents the road as a single line feature, its "DIR_TRAVEL" attribute is coded as "B" to allow travel in both directions. Am I missing some Netowrk Analyst capability that can help with this issue?