He/she was changing lanes without indicating.
'Freccia' = FRECH-chah — 'cc' before 'i' makes a 'ch' sound; double consonant.
Use in your police statement when the other driver's failure to signal contributed to the accident. Failure to indicate is a codice della strada violation that affects fault assessment.
'Mettere la freccia' (put on the indicator/turn signal) is the Italian colloquial expression for indicating. Formally it is 'azionare l'indicatore di direzione'. Failing to indicate when changing lanes is a fineable offence and is evidence of negligent driving.
Ha tagliato la strada senza segnalare.
He/she cut across without signalling.
'Tagliare la strada' = to cut someone off.
Ha invaso la mia corsia.
He/she crossed into my lane.
Lane invasion is a clear-cut violation.
Si è immesso in autostrada senza dare la precedenza.
He/she entered the motorway without giving way.
Merging failure — the entering vehicle always has to yield on Italian motorways.
Italian drivers have a mixed reputation for indicating — in urban areas, many drivers change lanes without signals. However, in accident liability disputes, failing to indicate is legally significant and is routinely flagged by traffic police.