Date: 201309
Local time of day: 1801-2400
Location: DEN.Airport, CO
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
ATC / advisory: Tower DEN
Second aircraft: Challenger Jet Undifferentiated or Other Model
Reporter organization: Government
Human factors: Distraction; Situational Awareness; Workload; Communication Breakdown; Confusion
Second reporter function: Captain; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airport; Environment - Non Weather Related; Procedure
Primary problem: Airport

Narrative: The landing air carrier aircraft did not exit the runway at the only high speed on Runway 7 and so was instructed to turn left at the next 90 degree taxiway. They responded in the affirmative and then proceeded to NOT exit at the next taxiway and continued down to the next exit. I was working Local 3 and 4 combined at Local 4; with arrivals to Runways 16R and 7. When the landing aircraft was not going to make the only high speed (B4); I stood to double check the distance and speed (using the RADAR; ASDE-X and windows) of the next arrival and determined that the spacing was sufficient for landing aircraft to go to B3; the next 90 degree taxiway; and for the aircraft on approach to continue. Then I went back to 16R to check the traffic there. As I turned again to check on the landing aircraft; a tower support beam between the windows was now in my view and I had to look around it before it was obvious that the landing aircraft was also not going to exit at B3 as instructed and replied. At the same time; they keyed up the radio and started to tell me so. This transmission blocked me from being able to transmit to aircraft on approach to go-around. When the landing aircraft finished speaking; I sent the aircraft on approach around. As I said this and watched the aircraft on approach appear to level off and start a slow climb; I turned to Local 2; in the opposite corner of the Tower and told them I was going around and he gave me the 185 heading; as I did not own any departure airspace for the go-around to go back to the TRACON for re-sequence. When the aircraft on approach did not reply to the go-around instruction; I said it again and realized that they were never going to go. As they were about in the flare; they asked me something about the traffic behind them and I said; 'Negative; two mile final.' They said they'd make either B4 (the high speed) or B3 and they landed.My role in this event; was not putting all my focus and priority on the landing aircraft and the approaching aircraft. Unfortunately; I let the previous hundreds of times that this same spacing was sufficient for aircraft making the next 90 degree exit; lead me to believe all was good again. In my experience; it had never occurred before that the aircraft did not make the next 90 after the missed high speed and instead continued down the runway. The landing aircraft's speed after missing B4 was slow enough; in my judgment; to have easily made B3.  Still; I should not have taken my eyes off them. In the time I stood up and judged the approaching aircraft's distance and speed and tended to the other traffic on Runway 16R and back; it was no longer 'all good'.The aircraft on approach probably also felt that the aircraft on the landing roll would make the first 90 after the high speed. When they did not; the aircraft on approach may have judged the distance and figured that they could keep it airborne until air carrier got down to the next taxiway. They fly into numerous small and sometimes uncontrolled fields and no doubt have witnessed or been involved in some operations that are technically not legal; but in their opinion; safe; how would they know? High speeds; high speeds; high speeds. The placement and lack of them at DEN is a bit of a sore spot for many controllers. The Runway 16R high speeds are placed so as to make that runway an issue every time we use it for arrivals. The first one is too close to the approach end and the second is too far down the runway. Like stated above; Runway 7 only has ONE! At minimum spacing of three miles between arrivals; these two runways can give a controller a work out when the traffic is constant.


Second narrative: First Officer was pilot flying and made a normal visual approach to Runway 07 at DEN. At our busiest phase of flight; touchdown; ATC issued instructions for us to exit the high speed and as I was trying to take control of the aircraft and the First Officer was trying to key the mic; we were too fast to make the turn at the high speed and I deemed it safer to continue past that exit. ATC then issued a non-standard clearance 'to turn left at the next 90.' I wasn't sure where the next 90 was located so while trying to look at my 10-9 chart and steer the aircraft; we missed the first available 90 degree turn to the left due to high residual ground speed. All the while; ATC told the Regional Jet behind us to go-around. We were too busy to notice; but as we turned off the runway at the very end; we could see the Regional Jet in the flare to land and was just touching down as we turned off.


Synopsis: A DEN Tower Controller and an air carrier pilot reported the air carrier failed to make a high speed turn off; so after the go-around command to an aircraft on approach was blocked; that aircraft landed. The Controller commented the DEN airport's general lack of high speed turn offs.