A new study by Comscore MobiLens shows that the use of mapping applications on mobile phones grew 44% in the year between April 2009 and April 2010. In just the three months between January and April 2010, close to 33.5 million mobile phone users in the US accessed a map application from their mobile phones.
So when do people actually access these applications? Here is a statistic from the study
Driving a car or another vehicle : 87.2%
Walking/Running/Biking : 17.2%
Using public transit : 16.7%
Smartphones definitely have played a huge role in this growth. Here is the number of smartphone users who were observed to have used a mobile map application during the month of April 2010 (and the YoY growth rate in brackets)
Total Mobile market : 16.773 million
Smartphones : 12.74 million (177%)
Feature phones : 4.03 million (-2%)