The lower regions and larger towns of the Alps are well-served by motorways and main roads, but higher <answer>mountain passes</answer> and byroads, which are amongst the highest in Europe, can be treacherous even in summer due to steep slopes. Many passes are closed in winter. A multitude of airports around the Alps (and some within), as well as long-distance rail links from all neighbouring countries, afford large numbers of travellers easy access from abroad.
What can be treacherous even in summer due to steep slopes?
mountain passes