Watch the Slow Blues Bass online guitar lesson by Jasper Mortier from 50 Blues Bass Licks You Must Know
Normally bassplayers tend to wait for things to happen; for instance with the soloist or with the drummer. But if you feel it and if it's musical: don't be afraid to take the lead every now and then and start driving a little for instance. If it's musical others will follow you too! If you felt others were slowing down for instance, talk about it after the gig/session or rehearsal. They often didn't notice it and felt you were rushing! Of course this can be completely the other way around too. Recording the session and listening to it later on can help too. Although there's no right or wrong. The feeling of the whole session is the most important thing and sometimes that involves a change of the tempo. Countless examples can be found in 50-ies Chicago Blues. So check out Muddy Waters or Jimmy Rogers for instance.