Hi,
It has not the same meaning what the traffic Jam..but the usage is same..as Traffic Jam is suppose to be said...when there is a huge Jam and vehicles are just stuck...and they even cant moving an inch ....
where as the Traffic crawling ..is said when there is a huge traffic but not exactly a Jam..the vehicles are not stuck ..but moving very slowly...and not necessarily it is used when there is situation like the traffic jam.It can be also used when there are some bad roads or some natural phenomenon..etc.
I hope you got my point..
Thanks
David.