It's different everyday. Depends on the bike I ride. How hard I want to ride. The wind, the temp, the traffic. Best average speed was 37.5kph for the 10.5km's but that was almost a TT like effort. Helmet camera video of my fastest ever commute is here. https://www.vimeo.com/6217227 On a regular day where I keep my heart rate between 120-140 I usually average 30-33kph. Thats on a cyclocross bike with knobby cross tires or a mountain bike with 1.5" slicks.

I'm about to hit the road with my Hardrock.
I was thinking a straight bar might get me a little lower than the riser bar.

How does it feel? Pics?
Interesting idea. Does it give you any better grip angle?

On my roadified Trek 7500 hybrid I can usually tick along at 18 -20 mph in calm conditions... I am running 700:28 Marathons at 90 psi.

This is also my average speed when I take the bike on longer uninterrupted rides.

I have two basic routes, one twice as long, but much flatter. Both are 90% on MUPs. That said my average speed (per bike computer) has been around 14 mph for this year. Fastest was close to 16.5 when I was riding with another cyclist and the slowest was 7.5 (six inches of snow with slush). My standard ride is an old steel rigid Raleigh M60 mountain bike with 26x1.75 Continental City Contact tires, fenders and rack. Loaded weight is around 40 pounds.

My current 10 commute (5 day) rolling average is now 21.2 (moving) 20.1 (elapsed)

I'm on a 40 lbs beach cruiser that's more than 20 years old. Pound for pound I think I'm a fast rider but my bike is a tank and I have to work really hard to get it going. Those roadside radar displays are really embarrassing for me. I hate it when I only get a 12 or a 13 mph on the speed display. I bet the passing motorists laugh at me and my puny score.

On my main commuter the bike computer usually gives my average speed in the 14-15mph range. This is a road touring bike set up for commuting, with 700x32 tires and all the K-Rap I carry she probably weighs 35lbs or more. On a crappy day riding into a headwind I may drop below 13mph. On a great day with a tailwind or with skinnier tires I'll beat 16mph.

I need to put a computer on my roadie SS, I just feel faster on that bike.

No computer on my bike. But my 9.2 miles takes me 50 minutes. This includes stoplights, etc. I'm at 11 mph.

I got rid of my computer because I found I kept looking at it to see how fast I was going and not paying attention to the road. but when I HAD it, I avgd about 11-13 mph... I'm glad I got rid of it, though.

My GPS says anywhere from 11-15 mph depending on which day and time of day, so I didn't answer. Wish I didn't have stoplights.

Dunno. I have a bike computer but I never really look at it, it's just there to tell me miles and let me know how many miles I'm getting from tires, chains, brakes, etc.

I can't imagine why I'd care how fast I'm going, really. I'm going however fast I am. I get there when I arrive.

It does take me about 34 to 39 minutes to finish my ride (depending on wind, etc), which is about 10.5 miles, so I guess that works out to...16 to 18 miles per hour.

This is kind of like asking what the largest fish you've ever caught is....almost impossible for people to avoid lying.

I do 13-14 mph for my 16 miles to DC each morning. Maybe 16-17 if I feel like it, maybe 11-12 if the wind is bad or I am tired as heck.

When my commute was only 4 miles I kept about 18-20 mph.....wasn't even enough to warm up.

40 miles round trip 2x per week on a mtb w/ schwalbe marathon cross tires. Ave. this summer for 36 rides has been 15.2 mph. Route is 1/2 Chicago city streets, 1/2 crowded bike path. Data from Garmin 605. The gps is addictive; can view the data in a myriad of different ways and makes it fun to compete with yourself.

I'm lucky if I can average 10 mph. But then, my rig weighs 55 pounds, unloaded; with the trailer attached, about 70 lb. Then when I have it laden with groceries and such, the whole thing can easily tip 100. And it's extremely hilly where I ride. Still, I have to admit, I really am the slowest thing on wheels.

1988 Schwinn Voyageur, 18 lb panniers and 50 mile round trip, some hills..13 mph seems to be a comfortable avg pace...

15 mi one way, 15-16 mph ave, cruising speed anywhere from 17 to 22, tons of stoplights, cyclocross set up for commute/light touring, 32mm tires, middle age engine.

No cycle computer yet, but I've tracked my 3.5mile commute with my iPhone & MapMyRide. According to it's gps calcs I'm getting 11-12mph.
Not sure if it counts stoplights or not, but...does it matter?

Riding an stock Trek Fx 7.3 (only add-ons are lights, and an under-the-seat bag)

I am at about 14 mph. This includes about 3 miles on a gravel bike bath. Commute is about 12 miles each way.

No computer... MapMyRun gives me anywhere from 13.5 - 15mph depending... I only encounter two stop signs and no lights so stopping is negligible. Real difference is direction...coastal living means a headwind every afternoon

No idea what my average speed is on my current bike. It doesn't have a computer on it yet. Even if it did, I still wouldn't be able to get an accurate measurement due to the G20 detour I need to make.

I put 8 - 10 mph based on my previous bike. I was averaging 9 - 10 mph based on the computer that was equipped on my 40lb Diamondback with 26x2.25 inch tires. A 3 mile trip took me roughly 30 minutes with all stop lights and signs factored in.

according to distance-time calculation i'm averaging around 13-14mph on a single speed shindig. it's though boston-cambridge though, so i hit a redlight about every 150 yards. it's a short commute though, only 6ish miles round trip and it only takes me 20-25 minutes round trip, wish i had a longer commute honestly, i just get going good when my commute ends.

17-19 mph ave if I am alone, not a lot, but compared to a year ago when I picked up cycling after a few years rest, I was doing 12-13mph "going flat out". This was helped by pulling both kids on the trailer for about 20 miles everyday, which in this case, average speed on the move goes to 13mph again, but its slowly increasing... 3 hills along the way helps the workout too