RSAP Frequently Asked Questions
    Questions about the types of problems that can be analyzed
Can you go past a non-traversable barrier and hit another fixed object, like water?
Yes.  Each type of hazard (see the Severity Worksheet) is associated with a capacity.  If the capacity of the hazard is exceeded, the vehicle will penetrate the hazard and continue on.  A tree located behind a guardrail, for example, can be struck if the vehicle has enough energy to exceed the capacity of the barrier and penetrate it.
Is the risk of head-on collisions factored into this analysis? 
No.  RSAPv3 is only concerned with run-off-road crashes so it does not account for any on-road crashes between vehicles.  One exception to this is median cross over crashes.  RSAPv3 does model cross-over crashes using the “median edge” special hazard.
Could explain what Alternative TL5 was chosen as the best option?
We are not sure what the question is referring to.  The webinar example only had four alternatives and the fourth was the one with the best incremental BCR.
How would you code in a drainage structure like a set of wingwalls on a box culverts?
Example number 1 in the User’s Manual covers exactly this problem.  The stream or water body is modeled as a water hazard and the culvert is modeled using the x-section.
Will repeated analysis using the same data result in identical results or will there be differences due to the statistical methodology used?
Yes, tthe results will be essentially the same (i.e., there may be some small round off changes from one run to another).  Unlike the earlier version of RSAP which used a Monte Carlo simulation technique, RSAPv3 is totally deterministic so you will get (essentially) the same answer each time.
If analyzing a paved, flush median would you recommend using the undivided or divided roadway option? 
You should define a paved flush median as a divided highway with the appropriate median width.  RSAPv3 encroachments begin at the edge of the lane so for an undivided road the left encroachments cross the centerline directly into the opposing lanes.
Are we given direction to now go beyond the clear zone? (i.e. water way in the example)
We are not implying that you must do the analysis for areas beyond the clear zone but RSAPv3 allows you to do so.  For example, you may want to find out if it is cost-beneficial to treat a hazard (e.g., a water hazard) that is just outside the clear zone even though the Roadside Design Guide does not require it.
After you run the analysis and then decide to change the traffic volumes (possibly as a sensitivity analysis)  do you just re-run the analysis?
Yes.  If you are interested in the same set of alternatives but under different traffic conditions you should re-run the analysis.  If you are interested in a sensitivity analysis based on the traffic volumes and truck percentages you can also use the Warrant Tool on (see the Analysis tab and check the “See Settings” check box.  The Warrant Tool allows you to increment the volume and percent trucks over a range so you can see how changing traffic conditions affects your analysis.  This was not covered in the webinar but the Warrant Tool is a very useful feature for looking at how you might develop warrants based on an RSAPv3 BC analysis.
For the Analyze>See Setting button, where it gives the trajectories number -- why? Should this be number that are generated from the traffic volumes and maybe vehicle types?
RSAPv3 collects a set of trajectories that best match the roadside terrain and highway geometry of the input data.  The  minimum and maximum number of trajectories settings allows the user some control over how large that set is.  The setting basically tells RSAP that you want to have between X (i.e., the minimum) and Y (i.e.., the maximum) trajectories for each departure point.  For example, let’s say you pick 10 for the minimum and 40 for the maximum (i.e., the defaults).  Let’s say RSAPv3 finds 25 trajectories that match your conditions well.  Since 25 is between 10 and 40 it will proceed.  Now, for each of the four encroachment types and each of the vehicle types it will generate 25 encroachments at points every 4 ft (i.e.,this can also be set by the user) along the segment.  Say you have a 1000-ft segment, 5 vehicles types and use all four encroachments and have a distance between encroachments of 5 ft. — RSAPv3 will generate 25x4x5x(1000/5)=100,000 encroachments/1000 ft.  RSAPv3 then takes the results and proportions them by the number of expected encroachments based on the Cooper data and the vehicle mix.