Narrative:

I was operating [the] flight to kiah. Upon arrival into houston; we were approximately 20 minutes early and the assigned gate of parking was still being occupied by the outbound aircraft. Once the outbound aircraft was pushed off; the gate we were cleared into the gate.the assigned gate was a self-park gate and as we approached the gate area we observed two wing walkers but no lead in marshaler. The self-park sign reflected no obstructions; so we proceeded into the gate as normal. We safely brought the aircraft to a complete stop at the proper parking/stopping spot and I set the parking brake.I looked over and saw that we had a gate agent to operate the jet bridge and shortly thereafter; the agent began moving the jet bridge towards the aircraft. Noticing that the left main brakes were rising in temperature; I released the parking brake to assist in the cooling process.I then continued with my post-flight checks and gathering my flight gear to exit the aircraft. Within a minute; I looked out my left side window and noticed that the jet bridge was within 2 feet of my aircraft but moving back towards the terminal. I immediately asked my first officer (first officer) if the aircraft was moving. Before he could even respond; I applied the toe brakes and set the parking brake. When I applied the toe brakes; neither me or my first officer felt the plane stop moving. So much so; we still could not figure out whether it was us rolling back or the jet bridge moving away from us.I then called houston operations and asked them if there was a problem with the jet-bridge or had our aircraft rolled back from the parked position. Operations responded by saying that the aircraft had rolled back out of the proper parked/stop position. They then advised us that they were bringing a tug over to pull us back into the proper parking/stop position.prior to the tug arriving; which was about 10 minutes later; the ramp supervisor contacted the cockpit via the external headset and asked me if I had released the brake without receiving to proper hand signal. I replied 'yes'. I did not see the hand signal prior to releasing the brake nor did I ever see a ramper signaling me or guiding the jet bridge driver.this was done because to my knowledge jet bridge movement does not commence until the rampers are in place to guide the jet bridge operator. This only happens after the aircraft has been chocked by the rampers and properly secured. With that said; I felt that my aircraft was safely chocked and secured and that I had either missed the hand signal or was never given one from the ramper while I was performing my post-flight checks and getting my stuff cleaned up.I have obviously fallen into the trap that many of my fellow pilots have fallen into which is the complacency of the rampers & jet bridge operators not adhering to procedures. It's been brought up by myself and previous crew members over the years; asking ramp operations to verify the aircraft is chocked. Multiple times we've been verified by operations over the radio; that the aircraft is chocked only after the rampers have walked away.it is now beyond clear to me that ramp procedures are not always followed and I cannot continue to assume that they have done their jobs as outlined. I will make sure that I physically see the hand signal or call operations like in the past to confirm that we are actually chocked and my aircraft I secured so to prevent any further miscommunication that could lead to an incursion and or safety issue.

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Original NASA ASRS Text

Title: Embraer Captain reported communications breakdown with marshalling crew at arrival gate resulting in aircraft rolling off gate due to no wheel chocks.

Narrative: I was operating [the] flight to KIAH. Upon arrival into Houston; we were approximately 20 minutes early and the assigned gate of parking was still being occupied by the outbound aircraft. Once the outbound aircraft was pushed off; the gate we were cleared into the gate.The assigned gate was a self-park gate and as we approached the gate area we observed two wing walkers but no lead in marshaler. The self-park sign reflected no obstructions; so we proceeded into the gate as normal. We safely brought the aircraft to a complete stop at the proper parking/stopping spot and I set the parking brake.I looked over and saw that we had a gate agent to operate the jet bridge and shortly thereafter; the agent began moving the jet bridge towards the aircraft. Noticing that the left main brakes were rising in temperature; I released the parking brake to assist in the cooling process.I then continued with my post-flight checks and gathering my flight gear to exit the aircraft. Within a minute; I looked out my left side window and noticed that the jet bridge was within 2 feet of my aircraft but moving back towards the terminal. I immediately asked my FO (First Officer) if the aircraft was moving. Before he could even respond; I applied the toe brakes and set the parking brake. When I applied the toe brakes; neither me or my FO felt the plane stop moving. So much so; we still could not figure out whether it was us rolling back or the jet bridge moving away from us.I then called Houston Operations and asked them if there was a problem with the jet-bridge or had our aircraft rolled back from the parked position. Operations responded by saying that the aircraft had rolled back out of the proper parked/stop position. They then advised us that they were bringing a tug over to pull us back into the proper parking/stop position.Prior to the tug arriving; which was about 10 minutes later; the Ramp Supervisor contacted the cockpit via the external headset and asked me if I had released the brake without receiving to proper hand signal. I replied 'yes'. I did not see the hand signal prior to releasing the brake nor did I ever see a ramper signaling me or guiding the jet bridge driver.This was done because to my knowledge jet bridge movement does not commence until the rampers are in place to guide the jet bridge operator. This only happens after the aircraft has been chocked by the rampers and properly secured. With that said; I felt that my aircraft was safely chocked and secured and that I had either missed the hand signal or was never given one from the ramper while I was performing my post-flight checks and getting my stuff cleaned up.I have obviously fallen into the trap that many of my fellow pilots have fallen into which is the complacency of the rampers & jet bridge operators not adhering to procedures. It's been brought up by myself and previous crew members over the years; asking Ramp Operations to verify the aircraft is chocked. Multiple times we've been verified by operations over the radio; that the aircraft is chocked only after the rampers have walked away.It is now beyond clear to me that ramp procedures are not always followed and I cannot continue to assume that they have done their jobs as outlined. I will make sure that I physically see the hand signal or call Operations like in the past to confirm that we are actually chocked and my aircraft I secured so to prevent any further miscommunication that could lead to an incursion and or safety issue.

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.