You've planned for months, got everything sorted and then BAM through no fault of your own local transport to your venue lets you down and causes chaos for you and your delegates.
Living and working in London I try not get too phased by travel disruptions as they happen quite often, however, for others they can be a nightmare which is why I do the following things before and during my event to make life easier for my guests.
About a week or so before an event is due to take place I do a bit of research to see if any planned engineering works are taking place. If there are and I think they might affect the event I will send out a quick e-shot to my delegates advising them to allow more time and offer alternative means of transport.
On The Day
Check the travel reports in the morning to see if there are any problems. Have a list of contact (mobile) numbers of your guests, if you've gathered them during the registration process, and if need be text people to let them know you're aware of disruptions and that you can delay the start of your event (if possible) to allow people more time to get there.
Letting your delegates know you are aware of problems put them minds at rest meaning they don't have to panic about possibly running late.