How to Predict/Forecast street's Traffic based on previous values?
This looks like a Time Series problem. So based on a variable's past values, you try to predict the future values.

Usually an "unheard of" problem with Spark, but you are in luck ; spark-ts library seems to be doing what you need, so you don't need to code your own using MLlib. I recommend you try it out and then circle back to something in MLlib if things don't work.

They have introduced a TimeSeriesRDD and once you can encode your data in this data structure (Note that this still behaves like a normal RDD), you can play around with the models available. For example, implementing the ARIMA model would be as simple as  - 

val arimaModel = ARIMA.fitModel(1, 0, 1, ts)


Hope that helps!