Transport data is crucial for transport planning and operations. Collecting high-quality data has long been challenging due to the difficulty of achieving adequate spatiotemporal coverage within a representative sample. The increasingly integrated use of Information and Communication technologies in transport systems offers an opportunity to collect data using non-traditional methods. Crowdsourcing applications are an example where a community of users shares information about their travel experience. However, crowdsourcing applications depend on a critical mass of users providing feedback. We conducted a large-scale field experiment to examine the effect of economic incentives (a lottery for free trips) and cooperation messages (asking users to help the community) to encourage users to share reports about bus stop conditions using a crowdsourcing app. We found that offering an economic incentive increased the participation rate almost three times compared to a control group, which did not receive any message. This positive effect lasted for several weeks but decreased over time, especially for users who had not made reports prior to the experiment. This incentive also increased the number of reports shared by users. Using a cooperation message, with or without the economic incentive, also increased the participation rate compared to the control group, but adding a cooperation message decreased the effect of a standalone economic incentive.