I have been wondering why cities don't publish their surveying data. They undoubtedly have this information? They should makeit available on the cities website as public record.
Taking the average (rise / run) isn't very accurate for severely undulating hills. I have some of these types of hills around my house and all the web routing systems give wildly different elevation readings.
Survey info?? if you really want to get that detail... just go to the City, County or State Public Works record office and ask for the as-built of the roadway(s). You might have to pay for copying. they are all public records. However, after 9/11, some of the data is more sensitive (like major structures).
On a steady even grade I count the feet gained in 1 mile then divide by 5280 feet in a mile and that will give you the grade % or just divide by 5 and thats close enough. 300 ft divided by 5 = 6% It's never as steep as I think.