Date: 201307
Local time of day: 1201-1800
Location: DEN.Tower, CO
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DEN
ATC / advisory: Tower DEN
Second aircraft: Dash 8 Series Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: First Officer
Human factors: Situational Awareness; Confusion
Second reporter function: Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
Result: Air Traffic Control Issued New Clearance
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: I was Pilot Monitoring during Flight XXX from XXX to XXX. There was an FAA Inspector on the jumpseat from XXX to DEN. We made slight diversions during arrival for weather South of DEN; but the approach and airport environment were in clear weather conditions. I cannot remember if we were given 34R from the beginning; or if that was a change in runway assignment from the original clearance. During the approach; at approximately 200 feet to 300 feet AGL; the Tower instructed us to go-around for 'traffic down field.'  Both the Captain and I thought they had issued this instruction to a similar call sign because it did not sound exactly like Company XXX. I remember that because I was frustrated with myself for missing the critical call and not questioning ATC sooner when; given the slow arrival rate at the time and our position; it was most likely for us. I did question ATC and was told for us to go-around.  All three of us in the cockpit were somewhat confused as to the reason since none of us saw any traffic at all 'down field.' We had assumed maybe it was a vehicle that we just couldn't see and completed the go-around and subsequent landing without incident. Today I received a call from the DEN Chief Pilot's office stating that there is going to be a meeting about the cause of this error and how to prevent similar occurrences in the future. I was told that there was a Dash 8 somewhere on Taxiway WB that posed a separation issue. To be honest; looking at the airport diagram; I was not aware; even though none of us saw an aircraft or vehicle; that one could not be present on the taxiway while another is landing 34R. I can clearly see the safety concern; but how far from the runway end is considered okay to taxi? Is WA; B4; B; or Runway 25 far enough for an aircraft to be on while one is landing 34R? This is not meant to be a sarcastic question; but I honestly don't know with an airport layout like DEN; how far out from the runway end is far enough. Once we landed; we discussed the go-around with the FAA Inspector and we were all still confused as to the reason why and repeated that none of us saw any traffic. The Inspector then stated that he would check into it more the next day and determine for his own knowledge the issues behind it. Better controlling and monitoring on the part of ATC; clearer go-around instructions especially when the aircraft is at such a low altitude; proactive control on the part of ATC so that the aircraft is not assigned a go-around that low; better knowledge on the crews; i.e. where it is acceptable to have an aircraft taxiing when you are landing; better observation of ground movement operations by the crew during the landing phase; and quicker questioning of ATC by the crew when not sure if the critical go-around call was for your flight.


Second narrative: We were cleared for a visual approach to 34R backed up by the ILS by Approach Control. After checking in with DEN Tower; we were cleared to land on 34R. At 100 feet AGL; the Control Tower told is to go-around. A normal go-around was completed. We were then switched to Departure frequency; who gave us RADAR vectors for a box pattern. We were then told to contact Tower. Upon checking in with DEN Tower; they cleared us to land again on 34R. Up until the Tower initiated go-around; the entire approach was normal. I have been informed that the go-around was due to our aircraft overflying an aircraft taxiing on Taxiway WB. Due to the angle of attack on approach; neither my First Officer nor I ever saw the taxiing aircraft.


Synopsis: Air carrier on short final to DEN Runway 34R was issued a go-around apparently because of a potential conflict with taxiing aircraft.