air, airline (esp. AmE), airplane (esp. AmE), automobile (AmE), bus, car, coach (BrE), jet, rail, sea, train
domestic (esp. AmE), foreign, international, overseas, transatlantic, world
long-distance
business, corporate (esp. AmE)
adventure (esp. AmE), leisure
holiday, vacation (AmE)
cheap, concessionary (BrE), discount (esp. AmE), free
first-class
return (esp. BrE), round-trip (AmE)
frequent
The job involves frequent travel.

extensive
interplanetary, interstellar, space
time

agency, agent, business, company, firm (esp. BrE), industry, market, service
an online travel agent

arrangements, plans
allowance (esp. BrE), budget, costs, expenses
insurance
document
itinerary, schedule (esp. AmE)
destination
Mexico's top travel destinations

ban, restrictions
time
The new road will reduce travel time to the airport.

season (AmE)
the holiday travel season

sickness (esp. BrE)
book, brochure, guide
literature, writing
writer
bag
companion (esp. AmE)

travel from, travel to
The price includes travel from Bangkok to Phuket.

a/the direction of travel (often figurative in BrE)
The party needs to set out a clear direction of travel for health care.

a/the means of travel, a/the mode of travel
The bus is their preferred mode of travel.

fast, quickly
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 to travel independently.

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

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

extensively, far, far and wide
information for the backpacker who wants to travel farther afield
a writer who travels far and wide

abroad, overseas
The job gives her the opportunity to travel overseas.

home
back, back and forth, down
He travels back and forth across the Atlantic.

north, northwards, etc.

across, along, around, at
to travel at the speed of light

between, by
We decided to travel by car.

around, from, into, round (esp. BrE), through
We plan to travel through Thailand and into Cambodia.

to, with
He travels with a huge entourage.

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

travel all over the world, travel around the world
travel back in time
In the film, he travels back in time to the '50s.

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

Travel is used with these nouns as the subject:
ball, convoy, eye, gaze, lorry, news, ray, signal, sound, traffic, train, wave

Travel is used with these nouns as the object:
circuit, country, distance, globe, highway, length, mile, road, route, world