Summarizing!

Summarizing need to be both concise and precise. It is understandable that summarizing is a shortened version of a text using your own words. 

Example :

Original : One of the most noticeable phenomena in any big city, such as London or Paris, is the steadily increasing number of petrol-driven vehicles, some in private ownership, others belonging to the public transport system, which congest the roads and render rapid movement more difficult year by year.

Summarizing ver. : Big cities have growing traffic problems.

But, remember that even when you summarize other's work, you still need to acknowledge it (citation).