EMB ERJ 190/195 ER/LR
Flight Crew Air Transport Pilot (ATP)
ATC Issue All Types; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew Took Evasive Action
Airspace Structure
We were in VMC conditions; and were advised of a VFR target crossing us; 500 ft below us. We were advised that the VFR traffic had us in sight and 'would maintain visual separation.'He crossed slightly off our left wing and was 400 ft below us. As he closed on us; we got a 'monitor vertical speed' RA. He then climbed slightly to 300 ft below us.Responding to the TCAS/FD command box; we climbed at approximately 100-200 feet per minute to 8200 ft until clear of conflict. We advised ATC and returned to 8000 ft when clear of the conflict.We had the traffic in sight; however; followed the TCAS RA guidance.The event occurred because ATC failed to provide traffic separation with VFR traffic. He advised us that the other traffic would assume responsibility for separation. However; the other pilot failed to maintain an adequate distance from us; setting off the TCAS.
EMB-190 Captain reported on descent to LGA he took evasive action from a VFR aircraft that was supposed to maintain visual separation.