Talk:401 / 404 / DVP
Just for interest, google pics at: 
Thanks for the interest Ojw. The satellite photo above (as of 2006-11-11) does not show recent construction that is reflected in the OSM map of this interchange. To be fair, the G-map layer is up to date.
So what is this interchange all about?
First, this is in Canada and drivers use the right-hand side of the road. I mention this because so many OSMers are from the UK. Wikipedia calls this the busiest highway in North America.
Highway 401 runs East-West across Toronto and is a tremendously busy stretch of highway. Through Toronto and serveral suburbs, the 401 has both collector and express lanes running in each direction. Transfer lanes between express and collector are less frequent than exits. Overhead electronic signs before these transfer lanes will offer status reports on the route ahead. An example might read "Express one right lane blocked. Collector moving slowly."
The Don Valley Parkway is the major North-South expressway on the east side of the city. A common experience on The DVP is long delays when trying to get out of the city before a long weekend. Most of The DVP is three lanes each way. North of Highway 401, the DVP becomes highway 404.
Highway 404 serves the northern suburbs and bedroom communities. One new feature of 404 is a short section of collector lanes, southbound from before Sheppard Avenue to DVP. Southbound traffic using the "collectors" here may exit at Sheppard, 401 eastbound, 401 Westbound (Collectors) or 401 westbound (Express). There is also a single lane to rejoin DVP southbound. 404 Southbound "express" traffic must proceed to DVP.
Another recent addition is the HOV Diamond lane. This lane requires two occupants or more per vehicle and is separated from the fast lane by additional paint. The HOV lane continues to DVP southbound and has a private exit from 404 southbound to 401 Westbound.
DVP northbound may proceed to 404 Northbound, exit to 401 westbound (Collectors only) or 401 eastbound (with a last minute choice for collectors or express).
401 eastbound, collector lane, drivers may continue on 401 eastbound collectors, select a left-exit transfer lane to the 401 eastbound express lanes, southbound DVP, northbound 404 "express" or northbound 404 including an agressive three-lane crossing in weaving traffic for the Sheppard Avenue exit.
401 eastbound express drivers may continue in the eastbound express, exit southbound to the DVP or northbound to highway 404. There is no option to exit 404 at Sheppard Avenue from the eastbound express lanes.
401 westbound collector lanes may continue in the westbound collectors, exit north to 404 including the Sheppard Avenue exit, or southbound on the DVP.
401 westbound express lanes may continue in westbound express, may exit to DVP southbound or 404 northbound (including Sheppard Avenue). Drivers may also use the transfer lane to get to westbound collector lanes.