Google has just added the ability to see traffic estimates by day and time for not just highways but also for many roads.
Google announced this on the Google Maps blog saying:
Starting today, if you’re planning a trip for which you anticipate traffic, you can find out what typical traffic is like on these arterial roads, rather than just on highways. Simply type in your starting and ending points to get directions in Google Maps, enable the traffic layer on the upper right hand side of the viewport, and then click “change” in the legend to switch from live traffic to Typical Traffic for these roads.
Here is a picture of a high traffic road in my area at certain times of the day and week:


The Google Maps team said on their Google+ page:
You can now get typical traffic for major roads as well as highways. This allows you to see what traffic will be like on different times and days of the week so you can properly plan ahead.
Pretty useful and glad this is back.
Google just also brought back live traffic data to Google Maps.
Forum discussion at Google+.

Comments:
Eugene
04/03/2012 01:49 pm
I've found their navigation tool very useful; I'm sure this will be equally useful. Thanks.
Cathy
09/11/2012 05:21 pm
This is helpful. I notice the time on suggested routes is still based on current traffic. At least I haven't found a way to make that change.
Oren Broshi
11/25/2012 02:38 pm
Did the suggested routes can be changed according to the day and hour i choose?