The wording is pretty simple and you'd think it would be easy enough to understand but this sign gets plenty of noisy criticism the pages of the Citizen's Voice.
Obviously it's a sign that comes into play in those areas of Highway One that split into four lanes, two in each direction. This is just south of Big Coppitt. 
And away stretch the four lanes across the light industrial suburb of Rockland Key, leading away to Boca Chica and ultimately Key West.
And that's the hump of the exit to the Naval Air Station on Boca Chica.
With the intrepid cyclist pushing on toward Key West:
These signs are everywhere along this stretch of Highway One and are largely ignored.
Traffic joins the highway just like any major freeway intersection on the mainland. And it requires traffic to merge from the right which is another complication for people with lane change phobias...
The thing about "slower traffic keep right" is that the wording doesn't say anything about speed limits or having private citizens enforce traffic laws. Some people like to sit in the passing lane and block people going faster than them which is a superb recipe for road rage. One gets to start envying the able cyclist pedaling along smoothly out of the traffic flow:
I spent a fair bit of time hanging out on the shoulder taking pictures: 
Not everyone gets the concept of staying on the right until you need to pass:
I get bored with clusters of cars piled up behind someone passing at one mile per hour faster than the vehicles being passed:
The bridge over Boca Chica Channel into Stock Island has some nice views over the water but it also has unmistakable instructions about keeping right, not that many people pay attention:
And even into the area were they are laying out the new sewer lines on Stock Island we see the same message repeated. 
Funnily enough what works for me is when the slowpokes are ambling along in the passing lane they open up the right lane for passing. I learned years ago in traffic school that 70% of tickets are issued to vehicles in the number one lane (the one nearest the median). I don't know if it still holds true, but I ride like it does. With cars trundling along in the fast lane I get to stay out of sight I hope.
By the time I got to Stock Island, taking pictures as I went, the intrepid cyclist was already there.
Right lane all the way, from Mile Marker 9 to Stock Island:
And here too the signs request that slower traffic....keep right, but It doesn't happen much. At this stage I figure i might as well sit in the right lane and take my time getting to North Roosevelt Boulevard,the main business route into the city:
You've got to figure the Florida Department of Transportation believes in this concept:
And in a state that has a law that says if you drive up to five miles per hour over the limit you can't get anything more than a written warning, you could be surprised by the seriousness with which they take the keep right rule:
As far as I'm concerned by all means trundle along in the left lane, all the more room for me where I am harder to spot...
