Custom vision service can also be used for Object Detection.
Object detection is used to determine if a particular object exists in a photo and where it is located within the photo.
The zip files above contain images you can use to train and test a Custom vision service model to detect runners and their race bibs using the instructions in this post to try it yourself using the training images provided
If you prefer to use the Custom Vision Service tool using code instead of the graphical interface, check out the Create an object detection model project with the Custom Vision .NET SDK Quickstart
If you want to create the model using the graphical interface and then call the model using your code, check out the tutorial on detecting Azure logos for a mobile app