MOVES has a "emission rate" calculation option that reports the emission rates for the 16 average speed bins used by MOVES for each hour of the day and additional emission rate output that may be of interest. See the MOVES User Guide for more details. The 2-day MOVES training course materials (available at https://www.epa.gov/moves/moves-training-sessions) include slides describing how to set up emission rate runs in MOVES, sample input files for setting up a run that would produce a table of running emissions by average speed bin, and sample output files.
If a user wants to estimate emissions at a specific intermediate speed, a linear interpolation can provide an approximation. For example, an interpolation between the rates for the 25mph and 30mph average speed bins can be used to represent emissions at a 28.3mph average speed.