Brighton and Hove Buses said that it was putting in place a series of measures to tackle recent driver shortages.
The company said: “Brighton and Hove Buses recently apologised to customers for the disruption in service due to driver shortage.
“The company been taking action to resolve this and has been working closely with other local operators to support specific services.
“We can confirm that from (Wednesday) 20 July until (Saturday) 10 September Compass Travel will be operating route 7X and from (Saturday) 23 July until (Saturday) 10 September Seaford and District will be operating route 77.
“At weekends open top and heritage vehicles will be used on route 77.
“Compass Travel and Seaford and District will be using their own vehicles, so please look out for the destination boards which will clearly identify the route number.
“All fares and scheduled times will remain the same and all ticket types will be accepted as normal.
“In addition to obtaining support from other bus operators, our colleagues at Metrobus in Crawley will be providing additional drivers.
“We also are looking at how we can speed up our recruitment and at hiring short-term ‘stop-gap’ drivers through an agency.
“We are planning to recruit a further 30 full-time drivers and currently have seven drivers in our training facility, with an additional 29 at various stages of the recruitment process.
“We employ more than 800 drivers and the team has been working really hard to cover additional shifts to keep our services running as fully and smoothly as possible under challenging circumstances.”
Managing director Martin Harris said: “I sincerely apologise to all our customers for the current dip in service levels and absolutely recognise the need to put our customers first as we always endeavour to do.
“I would also like to thank my colleagues who are making a tremendous effort to minimise disruption for our customers and express my appreciation to our fellow transport operators who are helping us.”