Date: 201308
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness
Second reporter function: First Officer
Anomaly: ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: I was taking Local 1 and was in a relief briefing when the prior coordination was not correct. A B737 was on a 7 mile final going 190 KTS and an MD80 was one half mile in trail going 250 KTS. Final coordinated with Local 1 to put the B737 on Runway 25R. When I took the position; and the B737 checked in for Runway 25L; I asked the pilot to verify they were for the left and not the right side. The B737 said they were for Runway 25L. I asked the previous Controller and they said; The MD80 was for the right. The MD80 [was] still on Final frequency was vectored to the south then back to the north directly over top of the B737 by 400 FT estimated. The B737 said they had an RA; I issued the traffic again for the second time and verified the B737 still wanted to land. Final said the B737 was suppose to be on Runway 25R but it would have been worst in my opinion if they were since the aircraft has to slow down to sidestep runways. The MD80 should have been broke out from the beginning. Also; TRACON normally calls and asks if they can put someone on the right and not the other way around. I feel this might have confused the control. If the first guy is too slow then you shouldn't slow them down more by sidestepping them. I recommend that assist one be open during traffic hours for coordinating reasons. Training was in progress on Final and the trainer should have maybe stepped in earlier.


Second narrative: While on final Runway 25L; another carrier's MD80 was behind us and cleared to do S-turns for separation. Approaching 1;200 FT AGL; we received a TCAS RA to descend. While complying; we noticed the traffic high to the left overtaking us. We advised Tower that we were complying with the RA and he advised us the other carrier's jet was breaking out to the south. It was a different Tower Controller than had originally cleared us to land. He asked us if we were cleared on the right or left. We advised him the left. He asked us if we would continue to complete the landing. We advised him yes; we would continue. [We] landed safely with no further incidence. A close one for sure. The Controller swap or training that was going on contributed to the event but the aircraft that are not maintaining separation should be made to discontinue their approach early so safe separation is not lost.


Synopsis: Local Controller described a pilot declared NMAC when the TRACON failed to establish appropriate speed assignments causing an overtake situation between two arrival aircraft.