How does biking affect your km walked?

It is just as going by car in my experience.
Just a minor distance gets calculated.
I use electric-bicycle though, so I can reach higher speed way easier.

Normally, i do not gather kilometers when biking, as the limit is 10.5 km/h. What helps is stopping each time a pokemon appears, trying to catch it, cycle on. This is exhausting, but it lowers average speed into the desired range.

If i just cycle and turn pokestops, catch pokemon free handed or one-handed without spin, i almost do not breed at all.
If i stop, catch and go, i collect kilometers.

I am bicycled almost 1650km out of my 2000km total. While I'm exhausted from 5km walk, I can bicycle 30-40km daily for a short period of time ( a week long event) and 15-20km daily basis. With good luck I'll get 75% of the total distance registered. Just paddle VERY casually. More casually than you've ever paddled. The speed is right, when you get 400-550m distance every 4min. If 300 or less, I've gone too fast and I need to slow down.

If your goal is to improve response time, you will be going too fast to log distance.

I always bike and it registrates about 5 km per hour.

I do this but it is tough to pull off just like the posts above say. I have an advantage though, all my riding is with two six year old girls who do their best to go the minimum speed. But I still have kept track of the actual distance that we normally ride as it equates to the cap for speed and distance. I also keep tabs on the time that distance is measured (which happens roughly 4 minutes and 10 seconds). This way if I hit that distance point and have not had updated distance I usually wait (typically only a few seconds) until it does.

This goes along with the question asked last week about mowing the lawn... In the case of mowing, it's most likely that you don't walk far enough between turns/course reversals to get any distance registered.
I tried it a few times last year, but then did a more comprehensice test this past Tuesday.
The longest straight line that I walk when mowing is 307 feet. I turn and reverse my direction and go back. I do this for almost 2 hours moving about 20 inches to the side each time I reverse direction. My Fitbit logged 5.42 miles. My phone using MapMyRun app logged 5.27 miles. POGO logged exactly 0.22KM. In this case, it's not the speed, it's the fact that you really don't move far enough in between distance registers by the POGO app.

I am biking right now. As long as it is not rain and you are in good signal range. Of course you have to lower your speed. But at the same time, you can enjoy the view and also it is quite safe to be slow.

I am biking whole winter and got 2500 km. It also depend on your phone! I buy new phone Honor 8 and i got better km:s. The distance on my work is 4 km and before i got 2-3 km put now 3-4 km.