A method for detecting a slow vehicle in a roadway, the method comprising: acquiring, from a camera of a user device, image data that depicts a view in a forward direction relative to a first vehicle, the user's vehicle, wherein the acquired image data represents an image of a second vehicle that is traveling in front of the first vehicle; obtaining first speed information of the second vehicle at a first time and at a first location, wherein obtaining the first speed information of the second vehicle comprises obtaining a current speed of the first vehicle, determining based on said image data of the user device, a change in distance over time relative to the second vehicle, and determining the first speed information of the second vehicle based on the current speed of the first vehicle and on the change in distance over time; determining, based on the obtained speed information, that a speed of the second vehicle at the first time is below a defined speed limit of the roadway at the first location; detecting, after a predetermined amount of time, that the second vehicle is traveling within a predetermined distance in front of the first vehicle; obtaining second speed information of the second vehicle at a second time and at a second location, wherein obtaining the second speed information of the second vehicle at the second time and at the second location comprises obtaining the second speed information using one or more sensors connected to or within the first vehicle, and wherein the one or more sensors exclude the camera of the user device; determining, based on the obtained second speed information, that the speed of the second vehicle at the second time is below the defined speed limit of the roadway at the second location; and transmitting, to an application server, the second speed information of the second vehicle at the second time and the image data. acquiring, from a camera of a user device, image data that depicts a view in a forward direction relative to a first vehicle, the user's vehicle, wherein the acquired image data represents an image of a second vehicle that is traveling in front of the first vehicle; obtaining first speed information of the second vehicle at a first time and at a first location, wherein obtaining the first speed information of the second vehicle comprises obtaining a current speed of the first vehicle, determining based on said image data of the user device, a change in distance over time relative to the second vehicle, and determining the first speed information of the second vehicle based on the current speed of the first vehicle and on the change in distance over time; determining, based on the obtained speed information, that a speed of the second vehicle at the first time is below a defined speed limit of the roadway at the first location; detecting, after a predetermined amount of time, that the second vehicle is traveling within a predetermined distance in front of the first vehicle; obtaining second speed information of the second vehicle at a second time and at a second location, wherein obtaining the second speed information of the second vehicle at the second time and at the second location comprises obtaining the second speed information using one or more sensors connected to or within the first vehicle, and wherein the one or more sensors exclude the camera of the user device; determining, based on the obtained second speed information, that the speed of the second vehicle at the second time is below the defined speed limit of the roadway at the second location; and transmitting, to an application server, the second speed information of the second vehicle at the second time and the image data.