air, bus, car, coach, rail, sea, train | foreign, international, overseas, world | long-distance | business | leisure | cheap, concessionary, free | first-class | high-speed | return | frequent
The job involves frequent travel.

space, time

agency, business, company, firm, industry | arrangements, plans | allowance, costs, expenses | insurance | document, documentation | itinerary | time
The new bypass will reduce travel time to the airport.

sickness | book, brochure, guide, writer

~ from, ~ to
The price includes return rail travel from London Victoria to Dover.

fast
News travels fast these days.

slowly | regularly
business people who travel regularly to the US

widely
She travels widely in her job.

freely
The dissidents were unable to hold meetings or travel freely.

independently
I prefer travelling independently to going on a package holiday.

together | separately
We had to travel separately as we couldn''t get seats on the same flight.

economy class, first class, etc.
I always travel first class.

far, further (afield)
for the holidaymaker who wants to travel further afield

abroad
The job gives her the opportunity to travel abroad.

home | back, back and forth, down, downstream
travelling back and forth across the Channel

north, northwards, etc.

be able/unable to | be free to | want to, wish to | be forced to, have to
Hundreds of hospital patients may have to travel long distances for treatment.

refuse to

across, along, around/round, between, by, from, into, through, to
We decided to travel by car. | We travelled through France and into Germany.

freedom to travel, go travelling
When I finished college I went travelling for six months (= spent time visiting different places).

travel light
She travels light, choosing to use as little equipment as possible.