You could try this, it should help a little bit, first make a backup copy of Sims3.ini which is located where you installed the game, something like C:\Program Files\Electronic Arts\The Sims 3\Game\Bin
In that file change the dynamic avoidance settings, I'm using some of these at half their default values:
[Config]
DynamicAvoidance_FieldRadius = 0.0
DynamicAvoidance_InactiveFieldLength = 1.5
DynamicAvoidance_MinNonIntersectingDistance = 0.12
DynamicAvoidance_FieldLengthPad = 0.3
DynamicAvoidance_StopDistanceMultiplier = 0.925