The trolley was moving left to express lane but the left trolley pole didn't switch to the left it stayed goin straight while the right pole switch leftward like it was suppose to there4 because the left pole didn't switch to the left turning wire the right pole slammed into the left pole of which the left pole was on the wrong wire. The right pole switch off to the left like it was suppose to, but the left pole stayed on the same strait wire and didn't switch leftward like the right pole did.