Highway 401
Macdonald-Cartier Freeway , Highway of Heroes
Route information
Maintained by Ministry of Transportation of Ontario
Length	816.6 km[1] (507.4 mi)
Existed	1947 (numbered in 1952)[citation needed]–present
Major junctions
West end	Highway 3 in Windsor
Major intersections	Highway 402 in London Highway 8 in Kitchener Highway 400 in Toronto Highway 62 in Belleville Highway 416 near Brockville Highway 138 in Cornwall
East end	A-20 towards Montreal, QC
Location
Country	Canada
Highway system
← Highway 400 → Highway 402

Highway 401 (named the Macdonald-Cartier Freeway) is a highway that extends across Southern Ontario, Canada. It is the longest 400-Series Highway in Ontario, and one of the widest and busiest highways in the world.^[2][3] Together with Autoroute 20, it is the road transportation backbone of the Quebec City-Windsor Corridor, along which over half of Canada's population resides. Colloquially, the road is known simply as "The 401", spoken as "four-oh-one". Since 24 August 2007 the stretch of highway between Toronto (from Highway 404 (Ontario)/Don Valley Parkway) and Trenton has been named the Highway of Heroes in honour of the Canadian soldiers who have been killed during the War in Afghanistan.

File:Carlb-McFreeway401-Mallorytown.jpg

Construction began on two portions of Highway 401 before the beginning of World War II: the new Kingston Road from Highland Creek (east of Toronto) to Oshawa, (modern day Former Highway 2A) bypassing the Kingston Road (Highway 2), and the scenic highway from Gananoque to Brockville, also bypassing a portion of Highway 2. The former was built because of heavy traffic between Toronto and Oshawa, and the latter to connect with the Thousand Islands Bridge (opened 1937). Until this time, the Thousand Islands Bridge terminated at Highway 2. ^[4] In late 1941 or early 1942, the scenic highway was opened to local traffic as a gravel road,^[5] and numbered Highway 2S, meaning "Highway 2 Scenic" (as opposed to the popular, but incorrect, idea of "Highway 2 South", as the road does lie fully south of Highway 2). Paving of the south side, the future eastbound lanes, was completed several years later.^{[citation needed]}

Construction of the first segment of the highway (originally designated Highway 2A) from Highland Creek (Scarborough) to Oshawa was initiated in 1938. The highway was designed to bypass a congested section of nearby Highway 2. Much of the grading and a number of structures were completed before the onset of the Second World War, at which time most of the construction work was shut down. This section was finally completed and opened to traffic in 1947. Until this road was extended east, it actually terminated at the Highway 35/Highway 2 interchange. Upon being extended east, the short dual carriageway connecting Highways 2 and 2A was re-designated Highway 35 (which is modern-day Highway 35/Highway 115).

During the war years, the provincial government undertook a number of surveys and studies to determine the most desirable route for the new limited-access highway.

The highway was redesignated "Highway 401" in 1952. The last segment, between Gananoque and Brockville, was completed in 1968 to bypass a section along the St. Lawrence River that included at-grade intersections and private entrances, now called the "Thousand Islands Parkway". The last at-grade intersection on the present alignment was at Joyceville Road, east of Kingston, which was converted to an interchange with the final 1968 construction.

During the late 1950s, the road was extended from Windsor to London, as an at-grade Super 2, and was twinned in the late 1960s/early 1970s (the segment from Windsor to Tilbury was completed as a four-lane freeway), with the eastbound carriageway being built first. This is still evident today, as many bridges over creeks and streams in the area have different ages and appearances. The section from Windsor to Tilbury was among the original sections built, from 1952-1958, with the Tilbury Bypass (from Exit 56 to Exit 63) being constructed in 1961, with the Tilbury-London section opening in 1963.

In 1964, Highway 401 was diverted from its former alignment in Windsor, Ontario along what is now Dougall Parkway, to its current terminus with Highway 3. The former alignment became Highway 401A (a secret designation, much like Highway 400A in Barrie). At this time, Highway 401 was also twinned from Windsor (interchange with Highway 98, now Provincial Road) to the eastern interchange (Exit 63) with Highway 2 in Tilbury, with two new lanes being constructed north of the existing lanes. The new carriageway became the westbound lanes, while the original two-lane carriageway became the east-bound lanes. This twinning from Windsor to Tilbury was completed in 1965. By 1968, all of Highway 401 was twinned to a minimum of four lanes.

In 1965, Premier of Ontario John Robarts designated Highway 401 the "Macdonald-Cartier Freeway", in honour of Sir John A. Macdonald and Sir George-Étienne Cartier, the Province of Canada's most important Fathers of Confederation, and in recognition of Canada's upcoming Centennial Celebrations in 1967. This name is found on maps and official documents, but seldom used in conversation or on modern road signs. A 1961 proposal to name the highway the "Leslie M. Frost Thruway" after the recently retired Premier of Ontario was approved by the provincial cabinet, but was not carried out.

When the September 11th Attacks occurred, the Ambassador Bridge connecting Windsor and Detroit was shut down as a result for roughly a week. This caused a nightmarish traffic backup, with trucks lined up all along Huron Church Road in Windsor, and along Highway 401 out to Belle River Road (a staggering distance of 34 kilometers/21 miles). One story posted in the September 12, 2001 issue of the Windsor Star told of a kind man driving to the McDonalds on Lauzon Road and Tecumseh Road and ordered 200 meals for stranded truckers, and even got the McDonalds restaurant to cover half the bill.

File:160 cfto salute 070822.jpg

On August 24, 2007, the Ministry of Transportation (Ontario) announced that the stretch of Highway 401 from Trenton, Ontario to Toronto will bear the name "Highway of Heroes" in honour of Canada's fallen soldiers, notably those who have died on duty in Afghanistan. This stretch of the freeway is often traveled by a convoy of vehicles carrying a fallen soldier's body with his or her family from CFB Trenton to the coroner's office in Toronto. Since 2002, when the first of Canada's fallen soldiers were returned from Afghanistan, crowds from all over the communities along this stretch of the 401 lined the overpasses to pay their respects as the convoy passes. The highway's designation as the "Macdonald-Cartier Freeway" will remain throughout the freeway's length. ^{[6] [7]} From the Don Valley Parkway to Trenton, large signs and several smaller reassurance markers with the new designation have been added to this stretch of the 401. Similar to the older and discontinued M-C Freeway shields installed in the 1960s, the King's Highway shields along with two shields with a poppy symbol (one with 401 designation and two with poppies with text Highway of Heroes and Autoroute des héros) appear after each on ramp along the route.

The section of Highway 401 between Windsor and London has become known as "Carnage Alley", particularly since 1988, when a long string of particularly violent and deadly accidents occurred in this section. These accidents have occurred because of the road's initial 1950s design, namely narrow lanes, soft shoulders, and narrow grass median which has proven to be insufficient in preventing cross-directional collisions. This stretch of highway is also one of the busiest truck routes in North America.

Highway 401 has been the site of Canada's deadliest automobile pile-up. An 87-vehicle pile-up occurred on the freeway just east of the Manning Road interchange and truck inspection center, during a thick fog on Labour Day. In response, the freeway is being given a massive upgrade. For more on this, read below. One of the more accident-prone parts of the freeway is at Exit 109 (Victoria Road, formerly Highway 21, now Chatham-Kent Roads 17/21). The freeway curves immediately east of the interchange and many people are not used to a curve near an interchange, particularly on the Windsor-London stretch of freeway, which has few curves.

Another result of this terrible accident is the implementation of province-wide "Emergency Detour Routes" (labelled "EDR" along freeways and exits). These EDRs are signed at exits, and along parallel county roads (which may or may not have been downloaded/former provincial highways) or major arterial roads in towns and cities to help motorists detour around an accident and find their way back to the freeway if a stretch of it is closed for whatever reason.

Highway 401 begins at Highway 3, 13 kilometres (8 mi) from the Detroit River on the outskirts of Windsor (not at the Michigan border as some mistakenly assume) and ends at the Quebec border, 815 kilometers (506 mi) away. There are 18 rest areas or service centres (oases) located along the route, allowing motorists to access services without leaving the highway. A plaque was erected at the Mallorytown oasis, located on the last section of the freeway to be completed, stating that the 401 was the longest non-toll freeway under a single highway authority in North America. (Today the Texas section of Interstate 10 holds this record.)

Major freeway junctions are located at these roads and highways: 402, Highbury Avenue (London), 403, 8, 6, 407, 410, 427, 400, Allen Road (Toronto), 404 and Don Valley Parkway (Toronto), 35 and 115, 416. Quebec Autoroute 20 continues the highway at its eastern end.

There are no direct interchanges with U.S. Interstate highways, but Interstates 75 and 375 in Detroit, Michigan, and Interstate 81 in New York State are each a short distance away, via Highways 3, the former 3B, and 137, leading to the Ambassador Bridge, the Detroit-Windsor Tunnel, and the Thousand Islands Bridge, respectively. Highway 402 also links Highway 401 to I-69/I-94 via the Bluewater Bridge in Sarnia, Ontario.

The 401 is one of the world's busiest highways,^[8][9] with an estimated Annual Average Daily Traffic (AADT) of over 500,000 in 2006, between the Weston Road and Highway 400 interchanges in Toronto.^[2] Due to its triple use as the main trade, commuting and recreational corridor in Ontario, 24-hour traffic volumes can exceed the 500,000 level on some days. The just-in-time inventory systems of the highly integrated auto industry in Michigan and Ontario have made the highway the busiest truck route in the world. Highway 401 also includes the continent's busiest multi-structure bridge at Hogg's Hollow in Toronto (four structures for the highway's four roadway beds).

The 401 is a strategically important highway in Canada, as it connects the populous Southern Ontario region with Quebec and Michigan, while also connecting to most other major highways in the province. The 401 also acts as a 'short cut' between Detroit and Buffalo, New York (via Queen Elizabeth Way and Highway 403), and is used by many American motorists for this reason. The highway also serves as the principal connection to Montreal and points east, including New England, becoming Autoroute 20 at the Quebec border. The border crossing at Windsor and Detroit is the busiest trade crossing in the world, and although the 401 itself does not physically extend the last few kilometres into Detroit, it is the only route from Toronto to Windsor and on to Interstate 75. A future expansion of the Windsor-Detroit border crossing, which will include a freeway bypass of the existing Highway 3, may result in Highway 401 having a direct freeway link to the border. Some 40 percent of Canada-US trade travels the highway, which is one-third of Canada's foreign trade, and 4 percent of all US foreign trade. However, it is not part of the Ontario section of the Trans-Canada Highway.

Today the stretch of Highway 401 that passes through the Greater Toronto Area ranges from 6 to 22 lanes.

The section that now runs through Toronto was a rural roadway that was entirely outside of the Toronto city limits when first opened, and was originally referred to as the Toronto Bypass. The new freeway attracted development all along its length. As the city's suburbs grew, it quickly became an urban commuter road, rather than a long-distance bypass route as was originally planned, leading to extensive traffic jams.

This was a problem/opportunity solved and built upon to some extent by implementing separate express and collector lanes, similar to the express/local set-up of the Dan Ryan Expressway in Chicago. Transfers, such as The Basketweave allow traffic to move from the express to collector lanes and vice versa.

Though Highway 401's collectors are intended more for urban commuters, they enjoy equal access to intersecting freeways as the express lanes do, such as at the junctions with Highway 404 and somewhat with Highway 400, so their use is not restricted to local traffic. It also facilitates road maintenance, as the MTO can to close off either the express or collector lanes for night repairs or upgrades. By contrast, the collector-express system on Highway 427 separate out two streams of traffic; the express lanes connect the QEW/Gardiner with 401 and exclusively lead to freeway-to-freeway ramps, while the collector lanes link up the arterials Highway 27 and Browns Line and have interchanges with local traffic.

By 1967 Highway 401 was widened from four lanes to 12 or more through Toronto from Islington Avenue to Warden Avenue.In the early 1970s the collector express lanes were extended to Neilson Road and eastward to Brock Road by 1997.

The main collector-express setup with a minimum 12 lane cross-section currently stretches from Islington Avenue to Brock Road. Highway 409 which branches off from Highway 401 just west of Islington to Toronto Pearson International Airport has been unsuccessful in diverting traffic volumes; the 10 lane segment between Islington and Highway 427 is highly congested as a result. The existing 401-427 interchange is considered one of the worst bottlenecks since it only allows eight lanes of traffic (four in each direction) to pass through the interchange. It initially only allowed six lanes of through traffic until a widening project was completed in 2005; a major reconstruction of the junction is needed to meet current demands estimated at five-to-six lanes.

An alternative plan to the collector-express setup was to construct a bypass of Highway 401. This project was revived in 1987 and opened in 1997 as the toll road Highway 407 ETR to parallel Highway 401 in the Greater Toronto Area.

In order to make sure drivers are not confused by signs appearing in other lanes, colours have been assigned to both Collector and Express Lanes. Collector lanes (handling traffic merging from and to exits) are blue while Express Lane signs are green. Due to the urban nature of the road, all signs are mounted overhead on gantries. The green signs list up to three upcoming exits (for example: Leslie St, Bayview Ave, Yonge St, 4km) However the mileage indicated on the signs do not indicate the actual distance to the next exit, they only indicate the distance to the next transfer to the collectors. Once in the collector lanes, the blue signs direct and inform drivers of the distance until the exit ramp (for example: Leslie Street, 1km).

File:Air France Flight 358.jpg

Highway 401 has a separate collector-express system in Mississauga between the junctions with Highways 403/410 and Highway 427. This was completed in 1986, concurrent with the expansion of the 401-403 interchange and the addition of two express flyover ramps and includes an eastbound collector-express transfer known as the "Tunnel." At 18 lanes wide this is the widest section of Highway 401, although at the present only nine lanes are designated for 401 through traffic (as express lanes) while the collector lanes serve as direct connections or ramp extensions from 403/410 to 427.

The existing 401/427 interchange remains a bottleneck to possible east expansion of this configuration that would link it up with the Islington-Brock collector-express system. Another choke point is at the 403/410 interchange since the 401 narrows down to eight lanes west of that junction. However, that junction has been designed with westward expansion of the collector-express system in mind; several prerequisite projects to accommodate widening from 403/410 to Mississauga Road were underway in the late 1990s, including a new interchange at Mavis Road and the reconstruction of the Mississauga Road and Derry Road overpasses.

Template:Future road In the 1950s, Highway 401 had initially been constructed as a four lane divided highway but the narrow grass median has since proven insufficient in preventing cross-directional collisions. In 1999, the Windsor-London stretch of Highway 401 was infamously dubbed as "Carnage Alley" after several fatal accidents, including an 87 vehicle pileup on Labour Day during thick fog that claimed seven lives just east of the Manning Road interchange and truck inspection center. Much work has involved replacing the median strip with an "Ontario tall-wall" concrete barrier and often an extra lane per direction.

Areas currently being upgraded are between Windsor and Tilbury, around the City of Kingston, the London area, from Stevenson Road in Oshawa to Highway 35/115, from Port Hope to Cobourg, and west from Cambridge towards Woodstock. This will be followed later by staged upgrades between Trenton and Belleville, and eventually the remaining sections between Cobourg and Kingston. Upgrading the final rural sections between Tilbury, Chatham and London, and from Cornwall to the Quebec Boundary remain beyond the 35-year planning horizon at this time.

On November 14, 2005, the joint Canadian-American committee studying the options for expanding the Windsor - Detroit border crossing announced that its preferred option was to directly extend Highway 401 westward, using a new bridge or tunnel to cross the Detroit River and interchange with Interstate 75 somewhere between the existing Ambassador Bridge span and Wyandotte. The exact route of this new highway connection has not yet been determined.^[10]

The Windsor Star has reported that the stretch of Highway 401 from Highway 3 (its western terminus) to where the road widens to three lanes per direction (3 km west of Manning Road) will remain as a four-lane route until a route to a potential new border crossing has been finalized. The MTO intends on upgrading this section, particularly its dangerous interchange with Highway 3 (sharp curves, poor lines of sight, aging overpass structure) when a new bridge and freeway corridor has been chosen.

Highway 401 is seeing a complete overhaul and expansion between the city of Windsor, Ontario and Tilbury, Ontario, in response to the 87-car pile-up that killed 8 on September 3, 1999. The road is being expanded from two lanes per direction with a narrow grass median to three lanes per direction (with concrete pavement), rumble strips, a concrete divider, and newer overpasses at Highway 77, French Line Road (St. Joachim Road), and two are planned for Puce Road, Belle River Road, and Former Rochester Township 3rd Concession Road (Eastern Lakeshore). ^[11]

The next phase for upgrading and widening Highway 401 in Essex County is currently under way and will stretch from Belle River Road/Essex Road 27 to Highway 77, widening each carriageway from two to three lanes, with a concrete barrier, and should be completed by November 2007. This construction zone is roughly the same size as the previous two, at 10.6 km in length. ^[12]

From (west) To (east)	Originally	Currently	Planned
3 km West of Manning Road (County Road 19) to 1 km east of Belle River Road (County Road 27)	2 narrow lanes per direction, dangerously narrow carriageways, dangerously narrow median, bi-directional onramps	3 lanes per direction, tall concrete barrier, separated onramps	Completed
1 km east of Belle River Road (CR 27) to 3 km west of Highway 77 interchange (10.6 km in length)	2 narrow lanes per direction, dangerously narrow carriageways, dangerously narrow median, bi-directional onramps	Under Construction/Widening/Upgrades	3 lanes per direction, tall concrete barrier, separated onramps
3 km west of Highway 77 interchange to 1 km east of Queen's Line (County Road 42) in Tilbury	2 narrow lanes per direction, dangerously narrow carriageways, dangerously narrow median, bi-directional onramps	3 lanes per direction, tall concrete barrier, separated onramps	Completed

Additionally, the Windsor South Truck Inspection Station has been upgraded to a commercial vehicle inspection facility^[13]

Highway 401 between Highway 35/115 and Stevenson Road (approximately 23.4km) has been resurfaced.

The Park Road exit is to be replaced by a new interchange at Stevenson Road in Oshawa. Construction began September 7, 2005. Currently, ramps from Stevenson Road to the Westbound 401 are open^[14]. This project is set to be complete by 2010 at a total cost of $65,097,000.00^[15].

Further west in Ajax Highway 401 between Carruthers Creek and Church Street has been widened from four to five lanes.

Highway 401 in London between Wellington Road and Highway 402 is currently being widened to six lanes. The improvements will include high mast lighting, a changeable message sign, advanced drainage systems and paved shoulders on both sides of the roadway. This, with the widening projects between Woodstock and Kitchener, will make Highway 401 at least six lanes wide from Port Hope to the Highway 402 interchange (From London to Toronto).

The very busy Wellington Road interchange will be completely redesigned and rebuilt as a parclo interchange. Construction began in 2006. This project is set to be complete by late 2007.

By 2009, a parclo interchange with Wonderland Road west of the partial Highway 402 interchange will be completed to provide better connectivity for motorists in London's southwest end to access Highway 401 west to Windsor.

Long term plans call for eight lanes and possibly a collector-express system through the city due to its increased use as a commuter road. However, these improvements are not planned until around 2020 and remain mid-to-long term goals for the Ministry of Transportation.

Originally	Currently	Planned
Lanes: 4 From Highway 402 to Wellington Road.	Lanes: 4 From Highway 402 to Wellington Road.	Lanes: 6 From Highway 402 to Highway 403.
Median: Ontario Tall-Wall.	Median: Reinforced Ontario Tall-Wall.	Median: Reinforced Ontario Tall-Wall with high mast lighting.
Paved inner shoulder, gravel outer shoulder.	No inner shoulder, paved outer shoulder.	Paved inner and outer shoulders with outer drainage system.
Rumble strips on outer shoulder	Rumble strips on outer shoulder	Rumble strips on both inner and outer shoulders
3/4 Cloverleaf interchange with Wellington Road.	401 Westbound on/off ramps open, eastbound closed.	Parclo A4 interchange with Wellington Road.

In the late Fall of 2005, the Ministry of Transportation of Ontario started a construction project to upgrade the current four-lane section of Highway 401 from four to six lanes from west of Oxford County Road 3 to west of Waterloo Regional Road 97 (where the next six-lane concrete-divided road begins) in the County of Oxford and Regional Municipality of Waterloo.

This is currently part of the last four-lane section between London and Toronto (stretching from Highway 403 Interchange in Woodstock, Ontario to Waterloo Road 97 in Kitchener, Ontario), but is being upgraded to 6 lanes plus an Ontario tall-wall barrier in the median. This is the first stage of upgrades of this final four-lane section.

In fall 2003, the widening of Highway 401 from four to six lanes from the Highway 8 interchange to Waterloo Regional Road 97 was completed. The Y-junctions with Highway 8 and Highway 403, opened in 1987 and 1990, respectively, were designed in mind to accommodate the widening of Highway 401 through Oxford and Waterloo.

Currently	Planned
Lanes: 4	Lanes: 6
Median: Grassed	Median: Ontario Tall-Wall
Rumble strips	Rumble strips (new)
Interchanges every 5 km or so	Interchanges every 5 km, plus two new emergency ramps
One slightly sharp curve north of Oxford Road (Oxford CR 29, Exit 250)	slightly re-aligned and straightened (completed and re-opened)

Aside from the addition of one lane per direction and a tall-wall barrier, two emergency ramp connectors that are intended to be used only during emergency highway closures and similar circumstances to permit traffic to move off the freeway (and emergency vehicles onto it) have been constructed. Built near Oxford Road 3 and Trussler Road, the ramps are an unprecedented addition to the Ontario highway system. onthighways.com source.

Other emergency accesses have been built in Essex County where the road was recently widened from 4 to 6 lanes, but these are gravel, and all are alongside overpasses, for use by ambulances, firetrucks, and police cars in emergencies only.

This is currently in stages, and will eventually close the 4-lane gap between the two 6-lane sections (London/Wellington Road-Woodstock/Highway 403 and Kitchener/Waterloo Road 97 (Cedar Creek Drive)-Toronto).

The first segment in Oxford County to see the upgrades is from Waterloo RR 97 to Oxford CR 3, with further upgrades planned from Oxford CR 3 to Highway 403. Several large upgrades will be carried out here:

• The interchange of Towerline Road and Middletown Line (Exit 236, just north of Highway 403) will be completely rebuilt and redesigned, as its current ramp configuration is extremely dangerous (short ramps with tight curves leading from an intersection just 30 feet/10 meters from the freeway, requiring a driver to "floor it" to get up to speed in time).
• The aging and sagging overpass structure at Towerline Road will be replaced, making this a long-overdue upgrade.
• The cloverleaf interchange with Former Highway 2 (Exit 238, which is the final remaining cloverleaf with two divided highways in the province) will be converted to a parclo interchange, as cloverleafs are no longer up to the Ministry of Transportation's safety standards (mostly from weaving). This will not be a disruptive construction contract, as the traffic volumes at the interchange are actually quite low (which is also why the cloverleaf interchange works smoothly) since former Highway 2 has been all but replaced by Highway 403 in the early 1990s. This will leave the Highway 4/401 interchange in London, Highway 62 in Belleville, and the former Highway 88/Highway 400 in Bradford as the last cloverleaf interchanges on a 400-series highway.

There are plans to widen the Mississauga stretch from six lanes to 12 lanes from the 403-410 interchange to the Credit River, and 10 lanes to Mississauga Road; this has recently been a major bottleneck due to the reduced capacity west of the junction. Actual construction on the expansion is slated to start in 2008 at the earliest, but for the last decade, numerous prerequisite projects have been undertaken.

The 403-410 interchange, which has been under construction since the 1970s until 1995, is designed in mind for westward expansion of the collector-express system (note the Highway 401 collector overpass structures crossing Highway 410, each of which have an additional lane which is currently unused. There is also an available right-of-way for a loop ramp from Highway 403 northbound to Highway 401 west and a direction ramp in the opposite direction, which is designed to improve access from Cawthra Road; this project would make the 403-410 interchange a full four-way interchange.

The Kennedy Road overpass, opened in the early 1990s just west of the 403-410 junction, is wide enough to accommodate expansion of the 12 lane collector-express system. The Derry Road underpass have been widened to accommodate this in the late 1990s. An interchange has been added with Mavis Road in 1999, which has been extended north to Highway 401 and beyond, and the overpass abutments are designed to allow future lengthening so fourteen lanes can pass under. In 2002, the Mississauga Road four-lane overpass was replaced with an eight lane structure that can span fourteen lanes, while the interchange ramps were also realigned to support higher speeds.

The main obstacles to Highway 401 expansion are the aging 1960s Creditview Road, McLaughlin Road, and Hurontario Street (the bridge structure and ramps were realigned in the 1970s from its original cloverleaf configuration) overpasses which will be demolished and replaced as part of the reconstruction.

Recently, the Ministry of Transportation also has mid-term plans to construct HOV lanes along Highway 401 from Mississauga Road to the 403/410 interchange. They have also announced long-term plans to further extend the HOV lanes further west to Milton.^[16]

To manage traffic, the Ontario Ministry of Transportation (MTO) installed the Freeway Management System - COMPASS, the most advanced of its kind in the world when it was deployed in 1991 by Delcan Corporation. Using a combination of CCTV cameras, vehicle detection loops and LED changeable message signs, the MTO Traffic Operations Centre can obtain a real-time assessment of traffic conditions and alert highway travellers of collisions and construction. The system currently stretches from Highway 403, Mississauga to Harwood Avenue, Ajax, and is likely to be extended westward and eastward as Highway 401 is reconstructed and upgraded.

• Highest Volume: 607,800 AADT from Weston Road (Exit 357) to Highway 400 (Exit 359) compared to 510,000 in 2003.
• Lowest Volume: 15,000 AADT from Dougall Parkway (Former Highway 401A/Highway 3B) (Exit 13) to Highway 3, "Bridge to U.S.A."

Listed below are notable cities along the route of Highway 401, from west to east. Bolded cities are officially-designated control cities for signs.^[17]

In the late 1980s to late 1990s, the stretch of Highway 401 eastbound around Milton had chevrons painted in the middle of each lane. Signs advised motorists to keep at least two chevrons apart, in essence warning them not to follow too closely.

Highway 401 is the busiest highway in North America, as well as one of the world's busiest. It is also the widest in the world in a total number of thru lanes with 18 in Mississauga.

Until the late 1990s, Highway 401 had blue signs near Windsor and the Greater Toronto Area stating nearby Interstate highways in the United States as "Advantage: I-75 I-80 I-90". Advantage was Mainline Automated Clearance System that processed trucks electronically. Trucks were fitted with transponders that relayed location, date, time, weight and axle information. This allowed trucks to bypass truck inspection stations if they already have been inspected. It also improved processing times at truck inspection stations.

An example of the sign:

ADVANTAGE

The following are a few of the major interchanges:

Location	km[1]	Exit #	Destinations
Windsor	0.0		Highway 3 west – Ambassador Bridge to USA
	2.6	13	Dougall Parkway – Detroit-Windsor Tunnel to USA
London	173.2	183	Highway 402 west – Sarnia
	179.1	21	Highbury Avenue – St. Thomas
Woodstock	225.3	235	Highway 403 east – Brantford, Hamilton
Kitchener, Cambridge	267.9	278	Highway 8 – Cambridge, Kitchener, Waterloo
Toronto	348.9	359	Highway 400 – BarrieModule:Jct warning: "road" parameter is deprecated
	364.9	375	Highway 404 – Downtown TorontoModule:Jct warning: "road" parameter is deprecated
Clarington	425.3	436	Highway 35 / Highway 115 – Orono, Lindsay, Peterborough
Leeds and the Thousand Islands	649.6	661	Highway 137 – Hill Island, Thousand Islands Bridge to USA
Edwardsburgh/Cardinal	708.6	721A	Highway 416 north – Kemptville, Ottawa

The service centres are located at the following points on Highway 401 and contain the following services *View Map:

Location	km	Direction	Fuel	Food	Other
Tilbury	61	Eastbound	Shell	Tim Horton's, KFC	unknown
		Westbound	Petro-Canada	Tim Horton's, Mr. Sub	unknown
West Lorne	144	Eastbound	Shell	Tim Horton's	unknown
	145	Westbound	Petro-Canada	McDonald's	unknown
Ingersoll	223	Westbound	Esso	Tim Horton's, Wendy's	Nicholby's Express
	225	Eastbound	Esso	Tim Horton's, Wendy's	Nicholby's Express
Cambridge	289	Eastbound	Petro-Canada	McDonald's	Picnic Area
		Westbound	Petro-Canada	McDonald's	Picnic Area Ellis Chapel
Mississauga Closed September 30, 2006	334	Eastbound	Shell	Tim Horton's, Wendy's	Nicholby's Express
Newcastle	444	Westbound	Esso	Tim Horton's, Wendy's	Nicholby's Express
Port Hope	453	Eastbound	Esso	Tim Horton's, Wendy's	unknown
Trenton	519	Eastbound	Petro-Canada	McDonald's	unknown
		Westbound	Shell	Tim Horton's, Wendy's	unknown
Camden East	591	Westbound	Petro-Canada	McDonald's	unknown
Odessa	604	Eastbound	Esso	Tim Horton's, KFC	unknown
Mallorytown	677	Westbound	Esso	Tim Horton's, Wendy's	unknown
	679	Eastbound	Esso	Tim Horton's, Wendy's	Nicholby's Express
Morrisburg	756	Eastbound	Shell	Tim Horton's, MacDonald's	unknown
Ingleside	761	Westbound	Esso	Tim Hortons, KFC	unknown
Lancaster	827	Westbound	Shell	Wendy's

Section	Lane Configuration
Huron Church Road/Highway 3 to Essex County Road 42	2 lanes in each direction 1 additional lane in each direction currently under construction
Essex County Road 42 to Wellington Road (London)	2 lanes in each direction 1 additional lane in each direction currently planned, stretch between Highway 402 and Wellington Road currently being widened from two to three lanes.
Wellington Road (London) to Highway 403	3 lanes in each direction stretch east of Highway 402 and west of Wellington Road Parclo currently being widened from 2 to 3 lanes
Highway 403 to Northumberland Street (Waterloo Regional Road 50)	2 lanes in each direction 1 additional lane in each direction currently under construction
Northumberland Street to Highway 410/Highway 403	3 lanes in each direction Stretch just east Mississauga Road to 403/410 interchange currently being widened to accommodate a future collector/express system
Highway 410/Highway 403 to Toronto Airport Basketweave	9 Lane collector/express system Eastbound 5 Express, 4 Collector 9 Lane collector/express system Westbound 4 Express, 5 Collector
Toronto Airport Basketweave to Highway 427/Eglinton Avenue	9 Lane collector/express system Eastbound 4 Express, 5 Collector 9 Lane collector/express system Westbound 4 Express, 5 Collector
Under the Highway 427 Interchange	4 lanes in each direction
Highway 427/Carlingview Drive to Highway 409	5 lanes in each direction
Highway 409 to Highway 400	7 lane collector/express system in each direction 4 Express, 3 Collector
Highway 400 to The Basketweave	8 lane collector/express system in each direction 4 Express, 5 Collector,
The Basketweave to Allen Road	7 lane collector/express system in each direction 4 Express, 3 Collector
Allen Road to Don River West Branch Hogg's Hollow Bridge	7 lane collector/express system in each direction 3 Express, 4 Collector
Don River West Branch to Yonge Street	6 lane collector/express system in each direction 4 Express, 2 Collector 1 additional collector lane in each direction currently under construction
Yonge Street to Bayview Avenue	7 lane collector/express system in each direction 4 Express, 3 Collector
Bayview Avenue to Highway 404/Don Valley Parkway	7 lane collector/express system in each direction 3 Express, 4 Collector
Highway 404/Don Valley Parkway to Kennedy Road	8 lane collector/express system in each direction 4 Express, 4 Collector
Kennedy Road to Markham Road/Highway 48	7 lane collector/express system in each direction 3 Express, 4 Collector
Markham Road/Highway 48 to Neilson Road	6 lane collector/express system in each direction 3 Express, 3 Collector
Neilson Road to Whites Road (Durham Regional Road 38)	7 lane collector/express system in each direction 4 Express, 3 Collector
Whites Road to Brock Road (Durham Regional Road 1)	7 lane collector/express system in each direction 3 Express, 4 Collector
Brock Road to Westney Road (Durham Regional Road 31)	6 lanes in each direction
Westney Road to Salem Road (Durham Regional Road 41)	5 lanes in each direction
Salem Road to Thickson Road	4 lanes in each direction 1 additional lane in each direction currently under construction
Thickson Road to Stevenson Road	3 lanes in each direction 2 additional lanes in each direction currently under construction
Stevenson Road to Port Hope	3 lanes in each direction 1 additional lane in each direction currently planned
Port Hope to Kingston western city limits	2 lanes in each direction 1 additional lane in each direction currently planned east of Burnham Street,Cobourg with 1 additional ane in each direction currently under construction west of Burnham Street.
Kingston western city limits to Sydenham Road (Frontenac County Road 9)	3 lanes in each direction
Sydenham Road to Montreal Street (Frontenac County Road 11)	2 lanes in each direction 1 additional lane in each direction currently under construction
Montreal Street to Highway 15	2 lanes in each direction 1 additional lane in each direction currently planned
Highway 15 to Quebec Border	2 lanes in each direction

• 400-series highways
• List of Ontario provincial highways
• Hogg's Hollow Bridge
• The Basketweave

• Ontario Ministry of Transportation
• Live COMPASS 401 Traffic Cameras through the Greater Toronto Area
• Photographs of the Macdonald-Cartier Freeway (Highway 401)
• Highway 401 at OntHighways.com
• Highway 401 History at thekingshighway.ca
• Highway 401 - the Story
• Truck Stops Within Ontario
• TravelCenters of America (operators of the Woodstock/Ingersoll Service Centers
• Highway 401 History