Interstate 5 and Washington Highway 539
interchange
Bellingham, WA, USA
Brian Schend's ideas for using roundabouts to fix
traffic signal's problems
Left:
The Seattle-Vancouver region. Right: City of Bellingham. On both
maps, a star marks the interchange location.
Interstate 5 and WA highway 539 ( Meridian St ) meet at a troubled
interchange in Bellingham, WA. I-5 runs NW/SE at this point. South of
Bellingham, I-5 goes to Seattle. North of Bellingham, I-5 goes NW
into downtown Vancouver using BC Highway 99. WA highway 539 goes
north from Bellingham into Vancouver's eastern suburbs using BC 13.
Within Bellingham, the highway is known as Meridian St. Outside
Bellingham, it's officially known as Guide Meridian Rd, but usually
called "The Guide."
Hwy 539 is a busy city street.
Despite this, the interchange is still essentially a diamond
interchange, usually used for rural low-traffic interchanges. It not
a classic diamond interchange, however; the offramp from south I-5
goes to the side road Macleod Rd instead of Meridian street. Also,
there are two extra ramps - one loop ramp from South 539 to South I-5
and one straight ramp from N I-5 to Bellis Fair Mall.
This interchange is outdated and has many problems, many caused
simply by using traffic signals:
The
problems
Problem 1: The
loop onramp from Southbound WA539 to S I-5 has too sharp a curve with
not enough acceleration space. Even sports cars are forced to enter
the freeway at 45 MPH, rather than the speed limit of 60. Large
trucks are forced to enter at about 30 MPH. The reason for the short
acceleration is the onramp right after this one. This acceleration
lane has to be short to allow room for the other freeway southbound
entrance. This other freeway entrance is straight and safe, but it is
only used for traffic going from North Meridian St to South I-5,
which is somewhat backtracking and lightly used. Traffic going S on
Meridian is not allowed to turn left there - they are all forced onto
the unsafe onramp in problem 1. Unfortunately, the lack of any
physical barrier means that occasionaly out-of-towners make this
illegal left-turn -- After yielding to opposing traffic and leaving
other cars behind them to wait.
Problem
2: Traffic going from North I-5 to North WA539 exits onto a
new right lane on WA539, which ends shortly north of there. At the
same time, traffic from the south that is turning right on Telegraph
road needs to merge right. That is, traffic from the freeway is
merging left at the same place where traffic from Meridian Street is
merging right. This is known as a weave, which results in traffic
jams and high accident rates. If fact, this intersection has the most
accidents of any location in the city of Bellingham. This is an
especially bad situation considering the heavy truck
traffic.
Problem 3: If you're
going south, it's perhaps even worse. The traffic light at Meridian
St and the N I-5 on- and offramp blocks traffic attempting to get
thru the overpass, especially southbound. Part of the problem here is
bad signal timing, but the large amount of traffic entering the
street at Telegraph Rd, just a little bit north, is too much for the
space between these traffic lights to handle.
Problem
4: Meridian St has a center 2-way turn lane. Altho a huge
improvement from roads in the past, it still is hazardous. Every
vehicle that turns left, whether at or between intersections, is a
potential severe crash. Traffic is also allowed to go straight across
Meridian St. When someone does so at the wrong time, it results in a
t-bone crash, the front of one car hits the side of another. This
type of crash causes enough damage to disable the car and usually
injures people in both cars. This means that a damaged car blocks the
roadway for the ambulances taking the victims to the hospital. The
way to eliminate these crashes is to replace the turn-lane with a
divider. This means vehicles are only allowed to make right turns,
except at major intersections. But, this requires allowing drivers to
make u-turns to get where they need to go. At traffic signls, three
lanes in each direction is required before it is possible for cars to
u-turn, and it is impossible for large trucks.
Problem
5: The most basic problem is that there
are too many cars for the intersections to handle. Since traffic
signal capacity is primarily determined by the width of the street
between signals, increasing capacity would require widening from two
to three lanes in each direction. This is unattractive, expensive and
dangerous for pedestrians who have so far to go just to cross the
street.
The Fix
I'm writing
this to show the many way that roundabouts are superior, and can fix
traffic at low costs. Therefore, in these fixes, you will not see any
new bridges, or even any new roadways, except for redesigned
intersections. You won't even see any widening. That's the point.
Roundabouts can fix the problems without the expense and trouble of
widening, new roads, and bridges.
Below, the problems are
repeated in gray, so you can see how the
roundabouts fix them.
Problem 1:
The loop onramp from Southbound WA539 to S I-5
has too sharp a curve with not enough acceleration space. Even sports
cars are forced to enter the freeway at 45 MPH, rather than the speed
limit of 60. Large trucks are forced to enter at about 30 MPH. The
reason for the short acceleration is the onramp right after this one.
This acceleration lane has to be short to allow room for the other
freeway southbound entrance. This other freeway entrance is straight
and safe, but it is only used for traffic going from North Meridian
St to South I-5, which is backtracking. Traffic going S on Meridian
is not allowed to turn left there - they are all forced onto the
unsafe onramp in problem 1. Unfortunately, the lack of any physical
barrier means that occasionaly out-of-towners make this left-turn.
After yielding to opposing traffic and leaving other cars behind them
to wait.
Fix 1: The reason
there is a loop ramp at all, is so traffic can go from southbound 539
to southbound I-5 with a right-turn. This is because traffic signals
do a poor job with heavy left-turn traffic. With a roundabout,
similar to shown below, cars could simply make the left turn instead
of using the loop ramp, and the dangerous loop ramp could be
permanently closed.
Problem
2: Traffic going from North I-5 to North
WA539 exits onto a new right lane on WA539, which ends shortly north
of there. At the same time, traffic from the south that is turning
right on Telegraph road needs to merge right. That is, traffic from
the freeway is merging left at the same place where traffic from
Meridian Street is merging right. This is known as a weave, which
results in traffic jams and high accident rates. If fact, this
intersection has the most accidents of any location in the city of
Bellingham. This is an especially bad situation considering the heavy
truck traffic.
Fix 2: The
solution to this problem is an old one, frequently used on freeways.
Simply require traffic entering from I-5 to yield first, instead of
getting their own lane. Meanwhile, traffic turning from Meridian
could already be in the right lane for the right turn, meaning they
wouldn't have to merge. However, fix three makes this a totally moot
point.
Problem 3:
If you're going south, it's perhaps even worse. The traffic light at
Meridian St and the N I-5 on- and offramp blocks traffic attempting
to get thru the overpass, especially southbound. Part of the problem
here is bad signal timing, but the large amount of traffic entering
the street at Telegraph Rd, just a little bit north, is too much for
the space between these traffic lights to handle.
Fix
3: Here's the real beauty of roundabouts. Traffic signals can
not adequately handle a busy six-way intersection no matter what.
Thus, it has to be a 3- or 4-way intersection. Roundabouts do just
fine at six-way intersections, as long as they're well-designed. What
do six-way intersections have to do with anything? Well, a roundabout
would allow these two 4-way intersections to be combined into one
6-way, as shown below. Now, everyone passing thru only needs to wait
once, to enter the roundabout. No one gets stuck between the two
intersections because there's only one intersection. In fact, a
single roundabout in Clearwater,
Florida replaced nine intersections and three traffic
signals.
PDF
Close-up
Problem 4:
Meridian St has a center 2-way turn lane. Altho a huge improvement
from roads in the past, it still is hazardous. Every vehicle that
turns left, whether at or between intersections, is a potential
severe crash. Traffic is also allowed to go straight across Meridian
St. When someone does so at the wrong time, it results in a t-bone
crash, the front of one car hits the side of another. This type of
crash causes enough damage to disable the car and usually injures
people in both cars. This means that a damaged car blocks the roadway
for the ambulances taking the victims to the hospital. The way to
eliminate these crashes is to replace the turn-lane with a divider.
This means vehicles are only allowed to make right turns, except at
major intersections. But, this requires allowing drivers to make
u-turns to get where they need to go. At traffic signls, three lanes
in each direction is required before it is possible for cars to
u-turn, and it is almost impossible for large trucks.
Fix
4: When you use roundabouts, there really is no excuse for not
building dividers. Even on a narrow crowded street, you can still
place a curb in the middle. Due to their round shape (duh), it is
very easy to make a u-turn. No widening is required to allow this.
And even on a two-lane road, roundabouts allow large trucks to
u-turn. Also, because of the merge-to-enter design, t-bones are
almost impossible at roundabouts. Instead, cars would collide going
at the same speed in almost the same direction (a sideswipe crash),
meaning damage would be minor and injuries unlikely. 70% less likely,
in fact. So, the roundabout eliminates serious crashes at the
intersections, and the median eliminates them between.
Problem
5: The most basic problem is that there
are too many cars for the intersections to handle. Since traffic
signal capacity is primarily determined by the width of the street
between signals, increasing capacity would require widening from two
to three lanes in each direction. This is unattractive, expensive and
dangerous for pedestrians who have so far to go just to cross the
street.
Fix 5:
Unlike traffic signals, roundabout capacity is based on the
size of the roundabout itself. That means by building large
roundabouts, you could increase the capacity of the street without
widening. This means safer crossing for pedestrians, and a more
attractive neighborhood than six lanes of cars.
Right-of-Way,
Environment and Cost
Roundabouts win in every respect.
Right-of-way refers to the land owned by the government for the
roadway. While this would require right-of-way for the roundabouts,
widening traffic signals require new right-of-way as well. But
widening traffic signals also requires new lanes for the entire
length of the street for the signals to do any good, therefore
signals require way more land than roundabouts.
The
environment is helped by building roundabouts for the same reason.
Not needing to widen the street allows you to leave the environment
alone. A portion of Meridian St runs right next to Spring Creek.
Traffic signals would require widening, and widening would require
relocation the creek. In addition, with four roundabouts in one mile,
traffic signals make cars sit and wait for about 10 minutes to get
thru the entire mile of street during busy times. Roundabouts would
reduce this to about 30 seconds, even in the busiest traffic. Less
cars idling means less air pollution. While traffic signals are an
ugly sea of pavement, roundabouts usually have attractive
landscaping.
Finally, on the surface, roundabout appear to
cost a bit more the traffic signals. But in reality, signals are much
more expensive. They require $3,500 a year in maintenance of the
electronics and control systems, plus $1,500 in additional electrical
costs. Traffic engineers often have to testify in court that a signal
malfunction didn't cause a crash, time and money he should have spent
on engineering. Roundabouts have no electronics or control systems,
and no chance to waste the engineer's time in court.. And, once
again, traffic signals require widening the road which is very
expensive. And this does not even begin to consider the costs of
crashes that signals have and roundabouts don't. With all factors
considered, we can't afford traffic signals. In fact, the worst
portion of this street could be fixed with the two roundabouts
described above, plus a roundabout at Bakerview Road to the north and
a median divider and new sidewalks for less than 2 million dollars,
and this would solve Meridian Street's woes for at least fifty years.
To put this cost in perspective, WSDOT
is spending 2 million dollars just
to study traffic flow on this street.
Summary
Many
in the United States seem to think traffic signals are the solution
to traffic problems. This "solution" increase crash rates,
causes long delays, requires enormously wide streets, and trashes the
environment. Clearly traffic signals are the problem, not the
solution. The solution is roundabouts, which could fix Meridian St
for less money than it costs to study it. So, as it turns out, once
you study roundabouts, you don't really have to study anything else
afterwards. Not to mention changing a signal to a roundabout
typically reduces all crashes by 50%, injuries by 70% and deaths by
90%. So you're ten times more likely to die at a signal than a
roundabout.
Americans are not used to roundabouts, and many
argue that we shouldn't take the risk to try something new. But in
this case, the real risk is not trying something
new.
________________________________________
Overhead
photos courtesy of City
of Bellingham GIS.
Highway sign at top of page courtesy of
Signmaker at http://www.kurumi.com/.