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Could someone please shed some light on how to describe the following idea?

After the car accident on the express way, the police went to the accident area and made a on-the-spot investigation.

i am in particular concerned with the underlined part. is it good? if not, can you provide a better version?

thanks a lot
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"On-the-spot investigation" is indeed OK.

It has the meaning
"an investigation performed at the crime scene / in the accident area"

It also implies it was done soon after the incident/accident, see definitions 1 and 2 here:
http://www.answers.com/topic/on-the-spot

Thus, if the investigation is protracted/delayed, I do not think we can say it's an
"On-the-spot investigation"

even if performed at the very spot of the accident.
Comments  
on-the-spot is very good.
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sounds good
 Marius Hancu's reply was promoted to an answer.
After the car accident on the express way, the police went to the accident area and made an on-the-spot investigation.
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