Because we know the trailer is running at 24 frames a second, we know exactly how long Sonic is running for.
The math isn’t all that complicated when it comes down to it.
These two data points allow Hill to calculate Sonic’s speed to be between 108 and 162 meters per second, or between 341 and 362 miles per hour, depending on the distance between the road marks, which vary slightly depending on where the road is located.
Kyle Hill of Because Science takes the brand new trailer for the Sonic the Hedgehog movie and, by using the dividing line on a two-way highway that Sonic runs down, where the dots have a fixed distance of three to four and a half meters, we can tell approximately how far Sonic is running.