Mobile cells had to be used this week to lock away prisoners in Northamptonshire when dozens of arrests swamped spaces in the regular cells.
As numbers rose, spaces ran out at Northampton, Corby and Wellingborough.
Of the 67 prisoners dealt with on Tuesday, 49 were arrested during the day and 18 were returned to custody.
To create extra space the cell bus, normally used at large-scale events, was at Campbell Square, Northampton, where the pressure was worst.
The bus is normally used for events with potential public order problems.
Although police admit the number of arrests posed a number of logistical problems, they stressed that they were problems which prove the force was doing its job effectively.