This is just a rather small modification of the rules, one I think it makes the "Speed" attribute a bit more relevant. A lot of monsters, and PC races have descriptions that say: They have quick reflexes and high speed, yet when in the game quick reflexes and high speed would come into factor, these creatures and races don't have a very big advantage. If you are bothered by that, use this houserule to change it.
Speed factor in initiation:
This rule is really simple. What you need to do, is to take the Speed attribute of each character NPC, PC and Monster as well. Every 5 increment in speed above 30 gives a +1 modifier to initiation, while every 5 increment below 30 gives a -1 modifier to intitative.
If a creature has flying and walking speed as well, use the one the creature is currently using. It is possible that an airborne creature is faster in air, than on the ground.
With this houserule you will be able to give a meaning to the speed factor even if you are not using a grid, or doing a chase scene.