One or more techniques and/or systems are provided for slowdown detection. Location data received from vehicles traveling a road is evaluated to identify a road segment associated with vehicle speeds below a threshold. A space-time diagram is generated, and location data associated with vehicles traveling the road segment are plotted within the space-time diagram. The space-time diagram is processed using a convolutional neural network to determine a probability that the space-time diagram illustrates a slowdown. If the probability that the space-time diagram illustrates the slowdown is greater than a threshold, then a notification of the slowdown is transmitted to one or more computing devices associated with vehicles that may encounter the slowdown.