Medium Transport
Flight Crew Air Transport Pilot (ATP)
Workload; Confusion; Communication Breakdown; Time Pressure
ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Runway
Flight Crew Became Reoriented
Human Factors; Airport
While landing on 30R in STL we were cleared to land and did such. Upon exiting the runway on high speed taxiway E2 tower told us to taxi via E2 then P and contact ground on 121.9. With the confusion of just exiting the runway; captain calling for an after landing check and getting a taxi clearance we became task saturated and I missed the call. The captain called back from what I recall; to the tower taxi via E2 then P and ground 121.9. Since standard operation is to get clearance to cross parallel runways from the tower I assumed that since we were instructed to contact ground we must have been cleared to cross runway 30L. Also during parallel runway operations tower will instruct planes to hold short of runways if they don't want them to cross.Since there is a lot of things that are happening while landing and taxiing we are dividing our attention amongst several things. This causes us to rely on things being standard in order for things to flow smoothly. Having a nonstandard way of doing parallel runway operations threw me as well as the captain for a loop. All other airports that I have been to have the tower controlling the runways because they are controlling what is happening on the runways. Once being cleared over to ground I felt that we were no longer dealing with runway crossings or runway operations. Since this is a busy time and there is a lot going on during landing and taxi I will personally make sure to slow down and make sure that calls are clear and concise as to what is to happen. Parallel runway operations are a busy and confusing place to be operating. Having a standard way of operations at all parallel runways would help to alleviate the confusion.
The cause of this event was the task saturation at the time of exiting the runway which was compounded by the tower communications. The second cause was the order in which the tower controller gave the call and since Papa extended across the parallel runway. At all other airports I have been to with parallel runways the tower controller maintains control across both runways and the releases the control to ground. I continued to stay with tower until crossing and never heard 'hold short' or any other instructions as we were approaching. I was not aware that this airport operated in a non-standard fashion in that ground control assumes control on parallel taxi way located in between parallel runways. At no time was our aircraft or any other aircraft in close proximity to each other. In the phone conversation I told the supervisor that at the other airports that tower maintains control of the runway environment until the aircraft crosses all active runways the relinquishes control to ground. It was then that he told me that that may be the way they do it elsewhere but that it was done differently in STL. That was the first time I was aware of the difference.  On our part we could slow down and clean up the airplane after crossing all runways and are solidly established with ground. On the part of STL controllers a return to standard procedures as outlined above would have prevented this as well. Had the tower controller started his call with hold short 30L followed by the rest of the instructions would have also prevented the confusion. Ground control may have been calling us to hold short but since we stayed on tower frequency we didn't get the clearance.
Air carrier flight crew reported a runway incursion when confused by taxi clearance after landing at STL.