Depending on the signal, I imagine that you have some kind of digital pulse that is high (or low) in case of a collision, you can measure the these times using a two edge separation measurement. LabVIEW ships with a example that you can use called:
'Meas Two Edge Separation.vi'
this is located in the 'Measure 2 Edge Separation.llb'
Hope this helps.
Met vriendelijke groet / Kind regards,
Karsten
Applications Engineer
National Instruments