The road beyond the bend

We counted bicycles from a sheltered doorway. At first the road was deserted; then the school gates opened and the traffic became continuous. A child with a yellow helmet stopped beside us to ask whether we were checking her speed. We explained that we only needed to record how many people passed and which direction they travelled. By the end of the hour, the page held columns of small strokes. It looked nothing like the busy scene it represented.

From the passage, select two words or phrases that describe how traffic changed during the survey.