1. As there was no bus service, I had to walk home.

2. There being no bus service, I had to walk home.
(Are both the same and grammatical?)

3. As there was no seat on/in the bus, I had to stand all the way.
4. There being no seat on/in the bus, I had to stand all the way.
(Are both the same? Do we have to use 'on' or 'in'?)

5. As it was rainy, I couldn't go on a picnic.
6. It being rainy, I couldn't go on a picnic.
(Are both the same and grammatical?)

7. As there were too many cars on the street, I couldn't go fast.
8. There being too many cars on the street, I couldn't go fast.
(Are both the same and grammatical?)

In all these sentences, the first of each pair is fine, and the second is clumsy. The second one in each is not incorrect, just clumsy and not used much.

In the first sentence in each pair "Because" is a good substitute for "As."

1. "As there was no bus service, I had to walk home." - This sentence is grammatically correct. It uses the phrase "as there was" to introduce the reason or cause for having to walk home.

2. "There being no bus service, I had to walk home." - This sentence is also grammatically correct. It uses the phrase "there being" to convey the same meaning as the first sentence.

Both sentences have the same meaning, but they use slightly different structures. The first sentence uses "as" to introduce the reason, while the second sentence uses "there being." Both are acceptable ways to express the cause-and-effect relationship.

3. "As there was no seat on/in the bus, I had to stand all the way." - This sentence is grammatically correct. You can use either "on" or "in" to describe the location of the seat. "On" emphasizes the surface area of the seat, while "in" emphasizes being inside the bus.

4. "There being no seat on/in the bus, I had to stand all the way." - This sentence is also grammatically correct. Again, you can use either "on" or "in" in this context.

Both sentences have the same meaning. They use the phrase "there being" to introduce the reason for having to stand.

5. "As it was rainy, I couldn't go on a picnic." - This sentence is grammatically correct. It uses "as" to indicate the reason or condition that prevented the picnic.

6. "It being rainy, I couldn't go on a picnic." - This sentence is also grammatically correct. It uses "it being" to express the same meaning as the previous sentence.

Both sentences are valid and have the same meaning. They introduce the reason for not going on a picnic using different structures.

7. "As there were too many cars on the street, I couldn't go fast." - This sentence is grammatically correct. It uses "as" to introduce the reason for not being able to go fast.

8. "There being too many cars on the street, I couldn't go fast." - This sentence is also grammatically correct. It uses "there being" to convey the same meaning as the previous sentence.

Both sentences have the same meaning. They explain the reason for the inability to go fast using slightly different structures.