Techniques for determining detection boxes representing objects in an environment using pixel clustering are disclosed herein. Autonomous vehicle sensors can capture data in an environment that may include separate objects, such as large and/or articulated vehicles. In an example, the data can include a plurality of pixels that are associated with a large object. A vehicle computing system can generate a detection box for each pixel of the plurality of pixels and can determine at least one averaged detection box representing the large object. In an example, the vehicle computing system can control the vehicle based in part on the at least one averaged detection boxes.