Running and Jogging

If your DM wants greater precision in a chase, the speeds of those involved in the chase can be calculated exactly. (But this is time-consuming and can slow down an exciting chase.) A character can always double his normal movement rate (in yards) to a jog. Thus a character with a movement rate of 12 can jog 240 yards in a round. While jogging. a character can automatically keep going for the number of rounds equal to his Constitution. After this limit has been reached, the player must roll a successful Constitution check at the end of each additional round spent jogging. There are no modifiers to this check. Once a Constitution check is failed, the character must stop and rest for as many rounds as he spent jogging. After this, he can resume his pace with no penalties (although the same limitations on duration apply).
If a jogging pace isn't fast enough, a character can also run. If he rolls a successful Strength check. he can move at three times his normal rate: if he rolls a Strength check with a -4 penalty, he can quadruple his normal rate; if he rolls a Strength check with a -8 penalty, he can quintuple his normal rate. Failing a Strength check means only that the character cannot increase his speed to level he was trying to reach, but he can keep running at the pace he was at before the failed Strength check. Once a character fails a Strength check to reach a level of running, he cannot try to reach that level again in the same run.
Continued running requires a Constitution check every round, with penalties that depend on how long and how fast the character has been running. There is a -1 for each round of running at triple speed, a -2 penalty for each round of running at quadruple speed, and a -3 penalty for each round of running at quintuple speed (these penalties are cumulative). If the check is passed, the character can continue at that speed for the next round. If the check is failed, the character has exhausted himself and must stop running. The character must rest for at least one turn.
For example, Ragnar the thief has a Strength of 14, a Constitution of 15, and a movement rate of 12. Being pursued by the city guard, he starts jogging at 240 yards a round. Unfortunately, so do they. His Constitution is a 15 so he can keep going for at least 14 rounds. He decides to speed up. The player rolls a Strength check, rolling a 7. Ragnar pours on the speed, increasing up to 360 yards per round (triple speed). Some of the guardsmen drop out of the race, but a few hold in there. Ragnar now has a -1 penalty to his Constitution check. A 13 is rolled, so he just barely passes. But one of the blasted guardsmen is still on his tail! In desperation, Ragnar tries to go faster (trying for four times walking speed). The Strength check is an 18: Ragnar just doesn't have any more oomph in him; he can't run any faster, but he is still running three times faster than his walking speed. The player now must roll a Constitution check with a -2 penalty (for two rounds of running at triple speed). The player rolls the die and gets a 4 — no problem! And just then the last guardsman drops out of the race. Ragnar takes no chances and keeps running. Next round another Constitution check is necessary with a -3 penalty. The player rolls an 18. Exhausted, Ragnar collapses in a shadowy alley, takins care to get out of sight.