A multicar elevator system comprising: a plurality of elevator sub-systems (110, 110', 110", 110′′′), each elevator sub-system comprising a shaft forming a loop path comprising a first vertical section and a second vertical section connected to each other with at least two horizontal sections, wherein the first vertical section in each elevator sub-system (110, 110', 110", 110′′′) is travelable upwards by at least one elevator car and the second vertical section is travelable downwards by at least one elevator car; at least one group controller configured to control the at least one elevator car in at least one elevator sub-system (110, 110', 110", 110′′′) among the plurality of elevator sub-systems (110, 110', 110", 110′′′); characterized in that the elevator system further comprising a reservation shaft accessible for the at least one elevator car from each elevator sub-system (110, 110', 110", 110′′′); and the at least one group controller is configured to control the at least one elevator car in the at least one elevator sub-system (110, 110', 110", 110′′′) among the plurality of elevator sub-systems (110, 110', 110", 110′′′) by: monitoring an operation of the elevator sub-system (110, 110', 110", 110′′′); and generating, in response to a detection of a predetermined condition in at least one of the elevator sub-systems, a control signal for enabling a use of the reservation shaft, wherein the predetermined condition is a malfunction of at least one elevator car; and communicating an availability of the reservation shaft to at least one elevator car being instructed to use the reservation shaft. a plurality of elevator sub-systems (110, 110', 110", 110′′′), each elevator sub-system comprising a shaft forming a loop path comprising a first vertical section and a second vertical section connected to each other with at least two horizontal sections, wherein the first vertical section in each elevator sub-system (110, 110', 110", 110′′′) is travelable upwards by at least one elevator car and the second vertical section is travelable downwards by at least one elevator car; at least one group controller configured to control the at least one elevator car in at least one elevator sub-system (110, 110', 110", 110′′′) among the plurality of elevator sub-systems (110, 110', 110", 110′′′); characterized in that the elevator system further comprising a reservation shaft accessible for the at least one elevator car from each elevator sub-system (110, 110', 110", 110′′′); and the at least one group controller is configured to control the at least one elevator car in the at least one elevator sub-system (110, 110', 110", 110′′′) among the plurality of elevator sub-systems (110, 110', 110", 110′′′) by: monitoring an operation of the elevator sub-system (110, 110', 110", 110′′′); and generating, in response to a detection of a predetermined condition in at least one of the elevator sub-systems, a control signal for enabling a use of the reservation shaft, wherein the predetermined condition is a malfunction of at least one elevator car; and communicating an availability of the reservation shaft to at least one elevator car being instructed to use the reservation shaft. monitoring an operation of the elevator sub-system (110, 110', 110", 110′′′); and generating, in response to a detection of a predetermined condition in at least one of the elevator sub-systems, a control signal for enabling a use of the reservation shaft, wherein the predetermined condition is a malfunction of at least one elevator car; and communicating an availability of the reservation shaft to at least one elevator car being instructed to use the reservation shaft.