Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

Hmm, disagree. The word involved is the past participle, and the words 'have been' is the past perfect tense of the verb 'to be', and the conjunction makes it the passive voice. The active voice would be 'I involved...', and 'I was involved' is the passive voice, whether it's 'I was involved', 'I have been involved', or 'I am involved'.

Unfortunately, it's not that simple. :) 'To be involved' is not a passive form but a description of a state, as in 'to be disappointed' or 'to be motivated'. 'To be' is here not an auxiliary verb as found in the passive voice but a full verb. 'Involved' is not a participle but an adjective or attribute, and 'have been' is the present perfect, not the past perfect.

As I said, it's borderline ambiguous and these distinctions run into one another to some extent in English, being more vague than in many other languages; e.g., you could say 'I am disappointed' and mean a perfectly active sense, or you could say 'I am disappointed by you', which is not clearly either active or passive. (Some people argue that this sort of thing is really a middle voice in English, but I think that's nonsense.)

However, the sense of the verb 'to involve' has much to do with the puzzle about our present example. It can take a passive voice, e.g.:

Active: I wasn't happy that she involved me in this.*
Passive: I wasn't happy to be involved in this by her.

* Note that this is merely a transitive use of the verb, which is sometimes confused with the passive.

Looking back at the 'disappointed' example above, consider how the same construction with the verb 'involve' then becomes passive:

I was involved by you.

You could add a clause like '... and now I can't get out' to make it perfectly clear. Where the sense of the verb can determine active or passive, there is no clear argument to be made that a particular construction must always have the same kind of result.

When one is 'involved' in something, one often has (had) no control over choosing whether or not to be involved--e.g., you might have to do a job you really hate as part of your regular work and become involved with people you'd rather have nothing do with, but have to stay professional. This distance is really what the driver above wanted to express, and it is this sense of the verb that plays into 'I have been involved in an accident'.

So, again, English is in some ways too reduced a language to make this completely clear, but I maintain that 'I have been involved in an accident' is active. :)