Urban freeway speed limits

[kphoger]

A Kansan's take on Minnesota driving habits:  They're terrible drivers, but nobody seems to care.

Take 494 around the southwest side of the Twin Cities, which I drive at least once a year.  Every time I'm there, I can encounter four lanes of traffic driving exactly the same speed; sometimes the left lane has someone driving there for absolutely no reason, often at slightly under the speed limit.  This doesn't seem to bother anybody.  Even if someone were to tailgate said left lane hog, it really wouldn't bother anyone, including the left lane hog.  Here, he'd chase the other guy down and shoot him.

[flowmotion]

They are probably just as deserving of that reputation as Minnesota, which was a lot more hit-or-miss to me. (Lots of rude behavior going on at my food stops, but the lady running the counter at the hotel we stayed at in Burnsville was top-notch.)

IMO Minnesotans tend to be overly-courteous while driving, in that they slow down and let people merge in front of them. This leads to a driving style where it's apparently considered OK to just cut you off whenever someone wants to change lanes.

Also, as kphoger says, they allow left-lane blockers to get away with impunity.

[Scott5114]

That may have been what the deal was with this giant traffic jam we got caught up in on I-35 north of Hinckley, MN. It was just a typical one lane closes, contraflow set up like you might find in Kansas or Oklahoma, but for some reason Minnesota managed to get it snarled up beyond all recognition. It took forever to get through.

[sp_redelectric]

In Oregon, 55-60 is the norm (not 65 though). Except in Portland, where a lot of places it's 50.

Portland speed limits:

I-5:  50 on the Interstate Bridge (also the only traffic light on I-5 due to the lift span), 55 between Interstate Bridge and I-405, 50 between I-405 and Terwilliger Curves (the southern I-405 junction will have variable speed limits coming soon; also the 55 section between 405 and Terwilliger is 50 for now due to construction), 55 south of Terwilliger Curves to I-205, 65 south of I-205.

I-405:  50 entire length (of less than four miles)

I-84:  55 I-5 to I-205, 60 I-205 to Sandy River, 65 east

I-205:  55 on the Glenn Jackson Bridge (most people are doing 75-80 here, it's wide open and very difficult to patrol), 60 from Airport Way all the way to West Linn, 65 West Linn to I-5

U.S. 26:  50 I-405 to Sylvan, 55 all the way out; includes a variable speed zone in Manning (west of Banks, junction with Oregon 47 north).  From Cornelius Pass Road west to the Oregon 6 interchange the actual travelled speed is much higher as this area is rural with only a handful of exits, but Oregon State Police and Washington County Sheriff's Office makes a lot of money here.  On the east side typically 35 Portland-Gresham, 55 east of Gresham to Boring and Sandy.

Oregon 217:  55 entire length (less than 8 miles)

Oregon 99W:  35 in Tigard, 40 in King City, 55 Tualatin to Sherwood (although for some strange reason a lot of people never make it past 50 which is absolutely frustrating), 45 within Sherwood, 55 over Rex Hill to Newberg

Oregon 99E:  55 between Columbia Boulevard and Marine Drive (well within Portland).  45 from the Ross Island Bridge into Milwaukie, 35 in Milwaukie, 40-45 south to Oregon City, 35 in Oregon City, variably 40 to 55 between Oregon City and Canby (a lot of speed reductions in this area due to it being a crash prone area, plus narrow lanes, few or no shoulder, poor visibility around curves)

Rural:  65 on Interstates (5 and 84), 55 on all other roads.  At least WSDOT got wise and allows 70 MPH driving on SR 14 east of Dallesport - it's actually faster to drive on two lane 14 than it is on four lane, divided 84.

[Interstatefan78]

Here in Newark, NJ  I-78 has a 55 mph speed limit from exit 56-58, but I-280 has a 50 mph speed limit from exit 15-17 due to the W.M. Stickel bridge.
Another note to Keep in mind is I-78 in Clinton,NJ has a 65 mph speed limit through an Urban area in northern Hunterdon county

Last I knew the speed limit on the Stickel bridge and its approaches was 40, then 50 on either side of the approaches.  The 50 mph limit has nothing to do with the bridge itself, but rather the geometry and traffic levels in Newark.  East of the bridge in Kearney I'd say it's very underposted and no one (including me) adheres to the 50 limit.  Also I'd say that it's a stretch to call Clinton an urban area.  It's a small town and nothing surrounding it.

I would say that Clinton is a small urban area because Union Twsp, and Clinton twsp hunterdon county, and Glen Gardiner, High Bridge, and Lebanon Boroughs surround it, and this will explain to why I-78 has exits 15,16,17 being separated by 1 mile apart from each other despite the 65 mph fines doubled corridor in an urban area.

[doorknob60]

I-205:  55 on the Glenn Jackson Bridge (most people are doing 75-80 here, it's wide open and very difficult to patrol), 60 from Airport Way all the way to West Linn, 65 West Linn to I-5

Did they finally raise it? Last time I drove it (no more thana year ago), I remember it being 55 the entire way from the Airport all the way down to West Linn, where it went up to 65. It was impossible for me to go that slow, I was naturally going around 67.

Rural:  65 on Interstates (5 and 84), 55 on all other roads.  At least WSDOT got wise and allows 70 MPH driving on SR 14 east of Dallesport - it's actually faster to drive on two lane 14 than it is on four lane, divided 84.

They put a 70 on 14 now? I seem to recall it being 65 the whole way, but it's been a while since I've driven that section. Good for them. Oregon's two laner speed limits are really a complete joke.

If you drive 55 anywhere in Central/Eastern Oregon, it's downright dangerous. I was riding with somebody from Bend back to Nampa, and he was driving about 55 (because he got a warning for going 70 on the way here, rediculous; probably targeted his WA plates...), and getting passed every couple of minutes, which is the most dangerous part of 2 lane highways, speed differential.

65 is essentially a minimum on roads like US-20 from Bend to Burns, and US-95, etc, even though it's only posted at 55 (though some highways will go their whole length without any signs telling you that, such as OR-78, with 55 signs only posted at the termini, even though it's like 70 miles long, from what I recall)

[mapman1071]

Phoenix has 55 on I-17 from Dunlap Avenue south around the bend to where it meets I-10 for the second time near Sky Harbor. Arizona 51 has 55 from the Glendale Avenue exit down to the Mini-Stack. Loop 202 east from the Mini-Stack is 55 but I forget for how far. Arizona 143 is 55 except for a short portion near I-10 where it's 45. On the outskirts, the new Loop 303 between Grand Avenue (US 60) and I-17 has a 55 mph speed limit for some silly reason, although the section skirting Sun City West does have a few at-grade intersections, such as at El Mirage Road.

As far as I know, all the other Phoenix-area freeways are 65.

Loop 202 is 55 from the I-10 (Papago)/AZ51 to the Loop 101 (Pima/Price), 65 from the Loop 101 (Pima/Price) to Loop 101 (Price),  55 from Loop 101 (Price) to I-10 (Maricopa) and 45 from I-10 (Maricopa) to Temp End at 40th Street/Pecos Road.

Loop 101 Is 65 From I-10 (Papago) to Loop 202 (Red Mountain) and 55 from Loop 202 (Red Mountain) to End at Loop 202 (San Tan)

I-10 Is 75 from Colorado River Bridge- MM 0 to Cotton Lane (Exit 124) ,65 From Cotton Lane to 35th Avenue, 55 from 35th Avenue to Baseline Road, 65 from Baseline Road to Queen Creek Road - AZ 347,  75 **  from Queen Creek Road - AZ 347 (Exit 164) to Cortaro Road (Exit 246), 65 From Cortaro Rd to Ina Road (Exit 248), 55 Ina Road to Craycroft Road (Exit 268), 65 Craycroft Road to Kolb Road (Exit 270) and 75 from Kolb Road East.

** After widening is complete (4 Lanes to 6) from Queen Creek Road - AZ 347 (Exit 164)  to Miracle Mile - AZ 77 (Exit 255) ADOT is planning to reduce the speed limit to 65 due to High congestion during Peak Hour Travel.

I-17 Is 55 From I-10 Split to Peoria Avenue, 65 from Peoria Avenue to Jomax Road (Exit 219) and 75 from Jomax Road to MM 245

[brownpelican]

Jackson, Miss.:
* I-20: 60 from MS 18 to MS 468
* I-55: 60 from north of Savannah Street to I-220; 50 within the Waterworks Curve.
* I-220: 70

[Some of us don't have Arial, and it makes our browser do funny stuff! -S.]

[StogieGuy7]

A Kansan's take on Minnesota driving habits:  They're terrible drivers, but nobody seems to care.

Take 494 around the southwest side of the Twin Cities, which I drive at least once a year.  Every time I'm there, I can encounter four lanes of traffic driving exactly the same speed; sometimes the left lane has someone driving there for absolutely no reason, often at slightly under the speed limit.  This doesn't seem to bother anybody.  Even if someone were to tailgate said left lane hog, it really wouldn't bother anyone, including the left lane hog.  Here, he'd chase the other guy down and shoot him.

Clearly, Minnesota and Wisconsin share the same inferior driver training program!  A drive through the Badger State also reveals drivers who have no understanding of the roles of different lanes.  Not to mention an incredible level of inattention - particularly pronounced when changing lanes.  Signaling?  Optional. 

But they are courteous: one R/T journey from N. IL to Door County, WI had us experience at least 4 or 5 close calls with bad Cheesehead driving; however, they all waved an apology each time.  As in "oh golly gee, I made a flub!"  There's nothing like driving 65 mph in the center lane and having someone just blindly pull right in front of you while going 50 mph.  On I-43 in a 65 mph zone.  If only they'd have sprung for some blood pressure pills as well!

[flowmotion]

That may have been what the deal was with this giant traffic jam we got caught up in on I-35 north of Hinckley, MN. It was just a typical one lane closes, contraflow set up like you might find in Kansas or Oklahoma, but for some reason Minnesota managed to get it snarled up beyond all recognition. It took forever to get through.

Yep, Minnesotans believe it to be "rude" to wait until the lane drop and do a zipper merge, like it's cheating somehow. Instead, they try to merge over as quickly as possible, even if it means blocking both lanes of traffic. 

[kphoger]

That may have been what the deal was with this giant traffic jam we got caught up in on I-35 north of Hinckley, MN. It was just a typical one lane closes, contraflow set up like you might find in Kansas or Oklahoma, but for some reason Minnesota managed to get it snarled up beyond all recognition. It took forever to get through.

Yep, Minnesotans believe it to be "rude" to wait until the lane drop and do a zipper merge, like it's cheating somehow. Instead, they try to merge over as quickly as possible, even if it means blocking both lanes of traffic. 

Interesting, then, that Minnesota often posts signs instructing drivers to form two lanes and then take turns at the merge point (zipper).

[Interstatefan78]

Here in Newark, NJ  I-78 has a 55 mph speed limit from exit 56-58, but I-280 has a 50 mph speed limit from exit 15-17 due to the W.M. Stickel bridge.
Another note to Keep in mind is I-78 in Clinton,NJ has a 65 mph speed limit through an Urban area in northern Hunterdon county

Many Speed Limit charts found online showing NJ has a 65 rural limit/55 urban limit are incorrect. I persume one organization posted it that way, and the rest simply copy it.  The vast majority of the Interstate/Limited Access highway network in NJ is classified as urban, and much of it has a 65 limit.  Heck, the 14 lane/4 section NJ Turnpike between Exits 11 & 12 is 65mph.

Those charts also show the max limit on other roads is 50 mph, which is incorrect as well.

55 is the maximum limit that is allowed to be posted on all roadways except where 65 mph has been authorized by the State. That is why NJ has no 60 MPH speed limits.
50 is the default speed limit in rural areas if nothing else is posted. 25 is the default speed limit in urban areas if nothing else is posted. However, I do not know if these definitions correlate strictly to the NJDOT classification maps shown online. If they do, there are a lot of very rural areas classified as "urban."

Right...they're the DEFAULT limits, not the MAXIMUM limits!  So depending on how you want to define the limit, the charts should be showing 65 mph for rural & urban, or 55 mph for rural and urban, but not 65 rural/55 urban.

The charts are clearly describing the maximum limits found on the highways (ie: http://www.motorists.org/speed-limits/state-chart; http://www.iihs.org/laws/speedlimits.aspx , which does correctly show a 55 max other road limit), and thus 65 should be shown for both.

As far as the default limits go, I can only think of one road in all my NJ travels that doesn't have a posted limit - County Rt. 632 in Mantua, NJ, between NJ 45 & Rt. 678)

I would say that the GS state parkway has 55 mph speed limit from exit 10-100 and also a 55 mph zone does exsts from exit 127-163, but Exits 100-127 and 163 to New York stateline are 65 mph, but NJ turnpike is 65 MPH from exit 1-12, but 55 mph from exit 12-GWB

[jeffandnicole]

I would say that the GS state parkway has 55 mph speed limit from exit 10-100 and also a 55 mph zone does exsts from exit 127-163, but Exits 100-127 and 163 to New York stateline are 65 mph, but NJ turnpike is 65 MPH from exit 1-12, but 55 mph from exit 12-GWB

Actually, I think you meant the GSP speed limit is 55mph from MP 80 - 100, not 10 - 100!  Below MP 80, it's 65 mph except on the Great Egg Harbor Bridge (45 mph) and where the traffic lights are located at "Interchanges" 9, 10 & 11 (50 mph).

Speaking off, the first of the contracts to start building the new overpasses there should be going out to bid soon.

[sp_redelectric]

Did they finally raise it? Last time I drove it (no more thana year ago), I remember it being 55 the entire way from the Airport all the way down to West Linn, where it went up to 65. It was impossible for me to go that slow, I was naturally going around 67.

Nope - it's still 55 as soon as you hit the Glenn Jackson Bridge; however I think ODOT (which maintains the bridge) finally put up a "Speed Limit" sign on the Washington side rather than the Oregon spec "Speed" sign.

When ODOT was given the authority to raise speed limits they came up with this ridiculous requirement that speeds could not be increased unless traffic volumes were low enough, and the area was close enough to a major trauma center (which all but ruled out most rural areas).  So all that happened was a few urban freeways increased from 55 to 60, such as I-84 between I-205 and Troutdale, I-5 through Salem and Eugene.  You're absolutely right, I-205 is the most modern freeway in Oregon and can definitely support a 65 MPH speed limit safely.

They put a 70 on 14 now? I seem to recall it being 65 the whole way, but it's been a while since I've driven that section. Good for them.

I believe there's a Speed Limit 70 sign located just east of the U.S. 97 junction at Maryhill...but it's been quite a while since I've been out that way.  It is definitely 55 west of there, with some areas with some very low advisory speeds (around Cape Horn and elsewhere between Washougal and Skamania, a lot of 25 MPH curves).

[Alps]

I would say that the GS state parkway has 55 mph speed limit from exit 10-100 and also a 55 mph zone does exsts from exit 127-163, but Exits 100-127 and 163 to New York stateline are 65 mph, but NJ turnpike is 65 MPH from exit 1-12, but 55 mph from exit 12-GWB

Actually, I think you meant the GSP speed limit is 55mph from MP 80 - 100, not 10 - 100!  Below MP 80, it's 65 mph except on the Great Egg Harbor Bridge (45 mph) and where the traffic lights are located at "Interchanges" 9, 10 & 11 (50 mph).

Speaking off, the first of the contracts to start building the new overpasses there should be going out to bid soon.

Speaking of which, the next New Jersey meet I plan to have will be down in Cape May...

[doorknob60]

I believe there's a Speed Limit 70 sign located just east of the U.S. 97 junction at Maryhill...but it's been quite a while since I've been out that way.  It is definitely 55 west of there, with some areas with some very low advisory speeds (around Cape Horn and elsewhere between Washougal and Skamania, a lot of 25 MPH curves).

It's been a while since I've been all the way to US-97, but I know between Bingen and US-197, it's 60 the whole way now (except in the towns), so I would assume it's at least 60 the rest of the way from US-197 to 97. West of Bingen I'm pretty sure it doesn't go above 55 though.

[swbrotha100]

I've driven around the valley freeways a LOT the past few years. Some have changed due to construction or end of construction. As of today (12/2/12) these are the posted "urban" limits in the Phoenix area:

-- I-10: 65 mph except around the Loop 303 construction zone in Goodyear, where it's 55 mph. 75 mph west of Verrado Way/Airport Rd in Buckeye, and 75 mph east of AZ 347/Queen Creek Rd.

-- I-17: 55 mph south of Dunlap Ave, 65 mph north to Carefree Hwy, 75 mph north of Carefree Hwy.

-- US 60: 65 mph on entire length of Superstition Fwy.

-- AZ 51: 55 mph south of Glendale Ave, 65 mph north of Glendale Ave.

-- AZ 143: 55 mph, 45 mph at each end.

-- Loop 101: 65 mph for entire length.

-- Loop 202: 65 mph for all except the connection to 40th St/Pecos Rd, where it's 55 mph, then 50 mph as it becomes Pecos Rd. There's a current 55 mph construction zone in Mesa between Guadalupe Rd and Power Rd, where ramps are being built for the future AZ 24/Gateway Fwy.

-- Loop 303: The current construction zone (I-10 to US 60/Grand Ave) ranges from 35 mph to 40 mph. When finished, this section should look similar to parts of Loop 202 in Mesa and Gilbert. 55 mph from US 60 to Happy Valley Pkwy. 65 mph from Happy Valley Pkwy to about a mile or two west of I-17. 55 mph, then 45 mph as Loop 303 connects to I-17 as a diamond interchange (Sonoran Desert Dr).

[lordsutch]

Atlanta:

- I-285 is signed at 55, not that anyone actually does 55 (it's usually either 65-70 or 20).  Allegedly the limit is going up to 65 soon, with variable signs on the northern side.
- Most radial interstates drop from 65 to 55 near I-285, although where they drop differs (I-20 west has a 60 mph zone near I-285, for example).  The 70-to-65 drop is relatively far out, compared to most other SE states.
- There is a 50 mph section of I-20 west of downtown.
- GA 400 is mostly 55 inside the loop and mostly 65 outside.  45 mph is signed through the toll plaza.  Stays 65 through the end of the freeway section.
- Ronald Reagan Parkway is mostly 50 mph, except at the eastern terminus where it's 45.
- Sugarloaf Parkway's freeway section is mostly 55, except at the southern end where it drops to 45 before a signalized intersection.

Gainesville:

- I-985 drops to 65 south of town and stays at 65 through its terminus (the 65 limit continues with the roadway north).

Augusta:

- I-20 and I-220 are 55 mph throughout Richmond County.

Macon:

- I-75 drops from 70 to 65 NW of Forsyth (and stays 65 between Forsyth and I-475, despite that section being rural in character).  Drops to 55 at Wesleyan Drive (near US 23), stays 55 through the city limits, then goes back to 65.  Unclear where 70 officially begins again (signage-wise, NB it drops to 65 just south of Hartley Bridge Rd; SB it doesn't go up to 70 until you pass Sardis Church Rd, probably because they forgot to (re)install the 70 mph signs southbound at Hartley Bridge after exit 153 was built).  It's 70 still through Houston and Peach counties, even though it passes through the Warner Robins MPO area and suburbanizing.
- I-16 is 55 mph to around milepost 3 or so, where it goes to 65; it increases to 70 near the Bibb/Twiggs line.
- I-475 is 65 mph throughout its length, even the portions inside Macon's city limits.
- Not clear what effect the municipal consolidation with Bibb County will have.

Athens:

- GA 10 Loop is at least partially 65; I haven't driven the full loop but I expect some of it is lower (particularly the non-freeway part).

Columbus:

- US 80 is mostly 65, except a short section at the east end where it transitions to a 45 mph surface arterial.
- Alt US 27 is also mostly 65, except at the terminus where it gets down to 50.
- I-185 is mostly or all 65; the southern few miles were previously posted at 55, but may have been increased now the widening project down to the Ft. Bennington interchange is done.

Valdosta:

- I-75 drops to 65 for a few miles, apparently for revenue enhancement.

Tifton:

- I-75 used to drop to 65, but no longer does.

It's been awhile since I went to Savannah or Brunswick, but my recollection is that I-95 does drop to 65 through these areas.  IIRC the local freeways (Truman and Veterans) in Savannah are posted at 55.

[TheStranger]

Most San Francisco Bay Area freeways have a speed limit of 65 MPH although there are some freeways with 55 MPH limits.  The lowest freeway speed limit that I know of is US 101 as it enters downtown San Francisco.  It has a 50 MPH limit.

There are two slower in SF itself I can think of:

- 35 MPH on Presidio Parkway/US 101 but that is due to construction and isn't permanent

- 45 MPH on the northernmost section of the Junipero Serra Freeway/Route 1, between I-280 in Daly City and the end of the freeway section at Font Boulevard.

Is the Central Freeway part of US 101 at 55 or 50?

[Brandon]

That may have been what the deal was with this giant traffic jam we got caught up in on I-35 north of Hinckley, MN. It was just a typical one lane closes, contraflow set up like you might find in Kansas or Oklahoma, but for some reason Minnesota managed to get it snarled up beyond all recognition. It took forever to get through.

Yep, Minnesotans believe it to be "rude" to wait until the lane drop and do a zipper merge, like it's cheating somehow. Instead, they try to merge over as quickly as possible, even if it means blocking both lanes of traffic. 

Michiganders tend to zipper together early but keep moving.  Chicagoans on the other hand tend to wait until the last freaking second and then bull, not zipper, their way in causing backups for miles.  I swear no one around Chicago has ever heard of zippering with traffic.

Also, these morons (Chicagoans and Downstate Illinoisans) seem to believe that you can enter a freeway at 40 mph.  In some areas (Detroit), that will get you run over and run off the road.  Always enter a freeway at speed (70 mph or so).

[tdindy88]

Unless you are following a semi onto the freeway, in which case you are generally forced to go at their speed up until you can get away from them. I go through a truck stop interchange on my way to and from work each day and have to contend with semis getting on the interstates. Unless you intend on hitting the back of their truck you have to go at their pace.

[jeffandnicole]

Michiganders tend to zipper together early but keep moving.  Chicagoans on the other hand tend to wait until the last freaking second and then bull, not zipper, their way in causing backups for miles.  I swear no one around Chicago has ever heard of zippering with traffic.

This is one of those traffic equations that is tough to understand, especially when people see it at the moment they are going thru the area.

For argument's sake, let's say a freeway travel lane can handle 2,000 vph.  And let's say a highway loses a lane, merging from 3 lanes to 2 lanes.  Regardless of where people merge, if there are 4,000 vehicles or less per hour in and around the merge area, traffic can merge and keep flowing.  If traffic volumes are greater than that, traffic will congest. 

It has nothing to do with people waiting until the lane ends. 

People will argue otherwise.  The only way to truly understand how this works is to watch video for literally hours on end of how traffic is flowing.  One would see that in both cases, traffic merge into the lanes that stay open early on, as well as traffic that remains in the lane that ends right up until the lane ends.  The main variable though is the overall traffic on the roadway.

[StogieGuy7]

That may have been what the deal was with this giant traffic jam we got caught up in on I-35 north of Hinckley, MN. It was just a typical one lane closes, contraflow set up like you might find in Kansas or Oklahoma, but for some reason Minnesota managed to get it snarled up beyond all recognition. It took forever to get through.

Yep, Minnesotans believe it to be "rude" to wait until the lane drop and do a zipper merge, like it's cheating somehow. Instead, they try to merge over as quickly as possible, even if it means blocking both lanes of traffic. 

Michiganders tend to zipper together early but keep moving.  Chicagoans on the other hand tend to wait until the last freaking second and then bull, not zipper, their way in causing backups for miles.  I swear no one around Chicago has ever heard of zippering with traffic.

Also, these morons (Chicagoans and Downstate Illinoisans) seem to believe that you can enter a freeway at 40 mph.  In some areas (Detroit), that will get you run over and run off the road.  Always enter a freeway at speed (70 mph or so).

There is some truth to this, although a recent journey along I-94 from IL to Detroit (and into ON) did reveal some pretty poor driving among Michiganders as well.  At times, it was amateur hour over there and I felt no shame in sporting my IL plates while passing through southern Michigan.

A surprising thing to me (and I had forgotten about this) was that I-94 is only 2 lanes in each direction for most of it's path between Benton Harbor and Ann Arbor (with a few exceptions here and there).  Combine that with a truck speed limit (60) that is 10 mph below that of cars and you have the recipe for lots of bottlenecks along a pretty busy - and somewhat overburdened - highway. 

What MI does that is MUCH better than the lunkheads in IL is set reasonable urban speed limits.  While a 55 m.p.h. speed limit on IL tollways is a total joke, urban interstates in the Detroit area set limits of 65 or 70 m.p.h. in all but the most congested areas.  Even in those zones, express lanes are marked at 70 m.p.h. while the local lanes are 55.  Very sensible.   Not like the idiocy of having a state-of-the-art roadway like the Tri-State Tollway, with an average speed of about 72 m.p.h., having a legal speed limit of 55 m.p.h. 

IL needs to "get real" as far as speed limits go.  70 miles per hour where it's reasonable and you go down from there.  MI is a good example, though - if anything - they need to hike the truck speed limit up a bit to 65.  A 10 m.p.h. difference is too much and it creates a hazard. 

[kphoger]

Unless you are following a semi onto the freeway, in which case you are generally forced to go at their speed up until you can get away from them. I go through a truck stop interchange on my way to and from work each day and have to contend with semis getting on the interstates. Unless you intend on hitting the back of their truck you have to go at their pace.

When I enter an on-ramp behind a slow-moving truck, I slow almost to a stop at the foot of the ramp in order to allow a gap to form between my vehicle and the truck, then I accelerate at my normal rate so that, by the time I get to the head of the ramp, I'm at a reasonable highway speed and can immediately pass the truck if there's a gap in the left lane.  If there's no gap in the left lane, then I slow down again, no worse off than if I'd stayed on his butt the whole time anyway.  If there is more than a couple of cars behind me, I abandon this strategy to avoid pissing them off; when through traffic sees four or five vehicles entering, they typically move over anyway.

Also, these morons (Chicagoans and Downstate Illinoisans) seem to believe that you can enter a freeway at 40 mph.  In some areas (Detroit), that will get you run over and run off the road.  Always enter a freeway at speed (70 mph or so).

I rarely enter the highway at more than 55 mph, and usually enter at around 45 or 50, simply because I avoid revving my car's engine that high for fuel economy.  I've never had any problems, and I've lived in both Chicago and downstate Illinois.  Sometimes, in fact, trying to enter at highway speed puts me right next to an 18-wheeler with no room to merge; I'd rather slide back along the truck at a slower speed and duck in behind him.  The only times I make sure to try and reach full highway speed on an on-ramp are when I know there's absolutely no wiggle room at the merge point–i.e., a hard curb line.

[agentsteel53]

it's tough to have a single unified policy for freeway entry.  as kphoger mentioned, sometimes one's acceleration curve precisely matches the location of an 18 wheeler in the right lane, so one has to accelerate a bit more slowly or quickly than anticipated to arrive at a gap in the rightmost lane and make a smooth transition.

usually, though, I try to hit the freeway already going at the speed of traffic.  if this involves a bit of revving, I don't mind it as much as kphoger does.  it's a very short acceleration and in the grand scheme of a full tank of gas, it's negligible.  If I'm merging onto the freeway more than 15-20 times during a tank of gas, I'm probably doing other things which are significantly more wasteful, like sitting in surface-level traffic.