You could say the buses are due every hour on the hour from 5 a.m. to 11 p.m.
This is a set phrase, so you should memorize it as a single vocabulary item.
That said, you can break it into two pieces to understand it better: every hour means "each hour"; on the hour means "at the beginning of the hour".
In other words, this refers to a time ending with o'clock or :00 .
When you put these two together, you get a phrase meaning "at the beginning of each hour".
ell.stackexchange.com/users/230/snailplane
snailboat's answer is very good, but if you are specifically looking for a specific single-word term to describe the "every hour on the hour" pattern, the word you want is hourly .
e.g., Buses arrive hourly from 5am to 11pm.
ell.stackexchange.com/users/53/Ken Bellows
Let's focus on the context of the example.
Try
"Buses go on the hour between 5am and 11pm."
Why did I pick "go"?
Because that's when it leaves .
"Go" is perfect because every non-native speaker will understand it (airport context), and it has a convenient and accurate double meaning.
"Arrive" could be confusing because someone might think the bus arrives at the destination at that time.
About other answers: Buses aren't normally "due", in conversation or formal texts.
They "run", "arrive" or just "come" (or, in England, should come!
;) )
and they often "go" or "leave".
I believe various spoken and written language usage corpii will back me up here.
As an English native, and teacher, I've never heard "at the top of every hour".
"every full hour" is confusing, "hourly" isn't specific enough, we're stuck with "on the hour" even if it's not so intuitive.
My second pick was "each hour" because it suggests more than "once per hour", but there's something unnatural about it...
ell.stackexchange.com/users/1744/techturbulence
I think there is not a single-word term which describes the succession of exact time like 1, 2, 3 o'clock, etc.
However, we do have a couple of phrases of common knowledge in this context, which are as follows: On the hour .
The phrase is indicative of both every hour and exact time as mentioned above.
So when we say "trains leave for London on the hour", it specifies not only every hour but also the exactness of time; that is 1, 2, 3 o'clock, etc.
Every hour on the hour is also correct.
Even if we drop every hour , it will give the same required sense.
In fact, the words "every hour" are emphatic here.
At the top of the hour .
I don't think this phrase fits in this context.
Sometimes,we hear on TV that we'll have a news update at the top of the hour.
What does it mean?
It means that we'll have a news update at the start of the next hour of time.
It does not mean every next hour.
In addition, this phrase is not much in use.
ell.stackexchange.com/users/9259/Khan
I would say "buses arrive every top of the hour".
ell.stackexchange.com/users/1640/user1307540
I would use every full hour .
There are some hits in the net: SE:
JavaScript:
How to do something every full hour?
Linguee
with a lot of examples.
I'm no native speaker, it may be a German 'false friend'.
It would be fine if somebody could confirm the term is right.
ell.stackexchange.com/users/38/knut
I was talking to my friend the other day about the airport bus timings, I was supposed to say    Buses are due at  6:00, 7:00, 8:00, 9:00  etc. (pattern like this the whole day between say 5 am to 11 pm)   Is there any specific term or way to describe the pattern?
Is there a specific term to describe time 6:00, 7:00, 8:00 etc
ell.stackexchange.com
<word-request><phrase-request>
ell.stackexchange.com/questions/6465
ell.stackexchange.com/users/466/Dude
"Every hour on the hour", "hourly" or "every top of the hour". Every hour on the hour works well. You can also use hourly and at the top of the hour.
Every hour on the hour works well. Hourly and top of the hour are options.