Riders have expressed to me a wide range of feelings over the years regarding interstate highways. Most riders I've met are willing to ride them but prefer the "back roads." Some riders have told me they simply hate riding on interstates and avoid them whenever possible. They often tell me they hate them because "they're boring," but will often later admit the higher speeds also make them very nervous.
Search across various motorcycle riding forums and you will find arguments from pro and anti-interstate riders, with a few in the middle, happy to ride either. I've always argued that riding interstates and other limited-access highways is actually safer than riding on full access roads, which have cross traffic and variable speed limits. However, it occurred to me that my argument is based on my experience and others I've spoken with. Likewise, the arguments I see in the forums are also based on the riders' relatively limited experience and deductive reasoning.
What we need here is data. For that, we can turn to the National Highway Traffic Safety Administration's (NHTSA) National Center for Statistical Analysis (NCSA). While we can find data specific to motorcycles, it doesn't appear we can locate the needed data regarding interstates versus other roads with the motorcycle data separated from that for other motor vehicles. The most recent relevant data I could find is in the NHTSA publication NHTSA Traffic Safety Facts 2009, page 55, Table 32: "Crashes by Number of Lanes, Trafficway Flow, and Crash Severity." (Ciick on the figure below to display a larger version of the graphic.)
We can consider interstates as having a trafficway flow of (a) divided, across (b) four lanes. Thus, we look in the third column ("Divided") and the "Four Lanes" row of each table for the data in which we are interested. Interstates appear to offer a significant, but relatively small safety advantage over non-divided, full-access roads.
This surprises me. I was certain that divided, multi-lane highways were much safer than the typical city street or country road. I was wrong. In fact, note how one and three lane divided roads look far more dangerous than the equivalent non-divided roads. I do find it hard to imagine a one lane divided road; it seems like an impossibility.
Unfortunately, none of this data allows us to make a comparison of the relative safety of riding motorcycles on interstates. However, if we look at the data for all traffic, we can find interesting NHTSA assessments of safety issues regarding interstates. For example, Table 25 in this same publication (p. 47) makes clear that the time of day you're on the highway matters a great deal: midnight to 3:00 a.m. on a Saturday or Sunday morning is consistently a very bad time. Rush hour is also a relatively unsafe time to be on the road. There are really no surprises here.
Where on the interstate system is also a key factor, obvious to anyone who has ridden on the D.C. Beltway or I95 just about anywhere. While we're on the subject of I95, NHTSA identifies the Florida section of I95 as particularly dangerous and published an entire report on fatalities on the D.C. Beltway.
NHTSA data also make clear that (1) the use of helmet reduces greatly the chance of being killed relative to not wearing a helmet and (2) consuming alcohol and then riding soon thereafter is a great way to reduce one's life expectancy.
So, I stand mildly corrected: driving on interstates in general is not much safer than other roads. Consequently, when I argue in favor of riding one, I will emphasis speed and convenience rather than safety.
I look forward to reporting to you on other tidbits I find in the NHTSA data.
Keep the shiny side up!
-The Long Rider
Other references:
NHTSA safety tips for motorcyclists
The NHTSA also offers an RSS feed for motorcycle-specific topics.