Version A -1942 on Cover, no WW II information.
Version B - 1942 on Cover, Coat of Arms removed, World War II information label on top of cover
Version C - No year on Cover, World War II information label on bottom of cover
Folded Dimensions: 3.5" X 9.5" 
Open Dimensions: 45" W X 19" H
Date Location: Front Cover & Legend
Cover Description: Yellow background with the word "ONTARIO" in white with black shadow effect.  Other lettering is white, black and red.  The provincial coat of arms is replaced on the cover by a warning re: World War II.
Date Code: Non-Applicable
Southern Ontario Scale: 1" : 18.5 miles
Northern Ontario Scale: 1" : 18 miles
Main Legend Side Features: Southern Ontario map as far north as Sudbury, Index of Southern Cities, Towns and Villages, Mileage Tables, Index of Lakes, Canadian Customs Regulations, Extract for US Tariff Regulations of Special Interest to Tourists, ", Synopsis of Fish & Game Law, front and rear covers
Opposite Side Features: Northern Ontario map, Index of Northern Cities, Towns and Villages, an Index of Lakes, 25 close-up maps of cities.
Mileage Tables: Highways No. 2  through to Highway No. 99 & The Queen Elizabeth Way
Compiled & Drawn By: D. Barclay. A. Hay, Chief Draughtsman
Prime Minister:  M. F. Hepburn
Minister: T. B. McQuesten, Department of Highways
Deputy Minister: R. M. Smith, Department of Highways
Copyright: Crown copyright is acknowledged, materials below are reproduced for non-commercial purposes.© Queen's Printer for Ontario, 2016. 
Director: Douglas R. Oliver, Travel and Publicity Bureau
Other: Lithographed by The Copp Clark Co., Limited, Toronto
Note:  The war effort interrupted the normal yearly production of the Official Road Map of Ontario.  As a result maps issued and clearly marked 1943, 1944 and 1945 are somewhat of a mystery.  Some collectors claim that the maps exist and are "out there".  Others state the maps marked with the 43, 44 and 45 individual years were never produced.  Based on the variation of covers for the 1942, the latter explanation would appear to be the truth.
Additional runs of the original 1942 map resulted in minor variations to the cover.... it seems that the original 1942 Official Map was produced as had been the established pattern - the year stated with no mention of the war effort.  A subsequent run of maps removed the Provincial Coat of Arms and included the year 1942 and the "War Label" near the top of the cover. In yet another later production, presumably well after 1942, the year was removed due to redundancy from the cover and the "War Label" was moved to the bottom of the cover.
 
For an interesting story about a small town named Swastika and the impact of WWII on it's name - please click HERE.

42A
Version "A"
My many thanks to Jason Jackson of Kamloops, B.C. for providing me with a scan of this 1942 edition of the Official Ontario Road Map and helping to unravel the production of Official Ontario Road maps during World War II. 
This cover does not include any information about the World War II effort and is essentially a continuation of the cover design that had come out first with the  1940-41 edition.
42B
Version "B"
rear42
42C Version "C"
Here is another variation of the same map.  The basic coloring is the same as the other 1942 maps, however, there is no year mentioned on the cover and the war effort label is at the bottom of the cover.
42 Northern Icon
Click on Above For Full Sized Image
42 Southern Icon
Click on Above For Full Sized Image
Title
NorthE
North Arrow Used On This Map
Southwestern