C172 pilot reported near midair collision with other traffic while on downwind for landing.

Narrative:

I was flying a cessna 172S to ZZZ. I had established communications with ZZZ tower on 118.5; and was flying the downwind leg for a right traffic pattern for runway xx at an indicated airspeed of 75 kts. There was one aircraft; a piper warrior; in the right traffic pattern behind me. My aircraft was equipped with a rear window; but the warrior was not visible to me during traffic scans. Tower instructed the warrior to make a left 360 because they were getting too close to me. I then looked over my left shoulder and saw the warrior at my 7:00 position; approximately 100 ft away at the same altitude. The warrior continued to turn left and separation distance quickly increased. I reported the near-miss to tower on the radio. My aircraft was equipped with garmin G1000 avionics; and the warrior was visible on my ads-B traffic display.I did not monitor my ads-B traffic display during the approach to land; relying exclusively on a visual scan. I was flying my traffic pattern at a speed which is perhaps slower than typical. The warrior pilot did not maintain visual contact with their assigned traffic to follow. Tower did not maintain adequate separation between aircraft in the traffic pattern.

Original NASA ASRS Text

Title: C172 pilot reported NMAC with other traffic while on downwind for landing.

Narrative: I was flying a Cessna 172S to ZZZ. I had established communications with ZZZ Tower on 118.5; and was flying the downwind leg for a right traffic pattern for Runway XX at an indicated airspeed of 75 kts. There was one aircraft; a Piper Warrior; in the right traffic pattern behind me. My aircraft was equipped with a rear window; but the Warrior was not visible to me during traffic scans. Tower instructed the Warrior to make a left 360 because they were getting too close to me. I then looked over my left shoulder and saw the Warrior at my 7:00 position; approximately 100 ft away at the same altitude. The Warrior continued to turn left and separation distance quickly increased. I reported the near-miss to Tower on the radio. My aircraft was equipped with Garmin G1000 avionics; and the Warrior was visible on my ADS-B traffic display.I did not monitor my ADS-B traffic display during the approach to land; relying exclusively on a visual scan. I was flying my traffic pattern at a speed which is perhaps slower than typical. The Warrior pilot did not maintain visual contact with their assigned traffic to follow. Tower did not maintain adequate separation between aircraft in the traffic pattern.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1678375
Time
Date	201908
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Other Traffic Pattern
Route In Use	Visual Approach
Flight Plan	None
Aircraft 2
Make Model Name	PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Person 1
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 10 Flight Crew Total 170 Flight Crew Type 150
Events
Anomaly	ATC Issue All Types Conflict NMAC
Miss Distance	Horizontal 100 Vertical 0