Freeport roundabout(s)

Another post on the Freeport Blvd Transportation Plan. See the category Freeport Blvd for other posts.

The city has proposed a roundabout for the intersection of Freeport Blvd and Sutterville Rd E. This is a good location for a roundabout, in part because there is so much space here already that a roundabout would not encroach on other uses.

Notes: I am calling the section of Sutterville Rd to the east of Freeport ‘Sutterville Rd E’ and the section to the west of Freeport ‘Sutterville Rd W’, but these names do not reflect street addresses, since this is all East Sutterville Rd. This post introduces the idea of protected intersections along Freeport, which apparently were not considered by the city in their planning process. For more information on this design, see protected intersections and Davis protected intersection.

First, what it looks like today. As you can see, there is a huge area of wasted space in the intersection

Freeport - Sutterville E intersection existing
Freeport – Sutterville E intersection

Second, the roundabout proposed in the plan.

Freeport - Sutterville E roundabout proposed
Freeport – Sutterville E roundabout proposed, north is to the right

This is a multi-lane roundabout. These roundabout designs are significantly less safe, for all modes of transportation (walking, bicycling, driving) than single lane roundabouts, and current roundabout practice is to only use multi-land roundabouts where they are absolutely necessary for the ADT (average daily traffic) to be designed for. Not the existing traffic, but the desired traffic. Not being a roundabout designer, I can’t say for certain whether a multi-lane roundabout is desired here. It is true that this intersection, and the stretch of roadway between Sutterville E and Sutterville W, combines traffic from both Freeport Blvd and Sutterville Rd. In the traffic counts diagram in the plan, this segment is shown as having the highest ADT of any section of Freeport, at 28,000 ADT. This does not mean the intersection needs to be planned for this volume, but it is an issue to be considered.

The possibly congested traffic flow is westbound from Sutterville E, south on Freeport, and then west on Sutterville W, or conversely, eastbound on Sutterville W, north on Freeport, and then east on Sutterville E.

So, yes to a roundabout at this location.

However, there are several potential improvements to the roundabout design.

  • Traffic north of the intersection does not need two lanes northbound or southbound. Freeport to the north is only two lanes (mostly at 3/2 design with center turn lane). It makes no sense to have the segment to the north with unneeded capacity.
  • There is 1060 feet of roadway south of the roundabout for southbound traffic to merge right for a turn to Sutterville to the west, or left to continue south on Freeport. Merges do no need to happen within the roundabout. That means the west side of the roundabout need only be one lane. Or, the west side right hand lane can be a bypass lane, with no interaction with the other lane providing the roundabout function.
  • Similarly, there is ample space northbound for merging, so the lane that goes from Freeport northbound to Sutterville to the east can be a separated or bypass lane, with no interaction with the other lane providing the roundabout.
  • Proposing something way outside the box, traffic from Sutterville E with Sutterville W could be routed through the park, rejoining Sutterville to the west of the Freeport – Sutterville W intersection

So, why is roundabout in the post title potentially plural? Because I think either roundabouts or protected intersections should be considered for the intersection of Freeport with Sutterville W, and Freeport with Fruitridge.

First, what Freeport – Sutterville W intersection looks like today.

Freeport - Sutterville Rd W intersection existing
Freeport – Sutterville W intersection

Second, the plan proposal. It is very much like the present configuration, the differences being the the southbound bike lane is merged across the right hand turn lane rather than being dropped, the bike lanes are partially separated bikeways (meaning at least vertical delineator ‘protection’ and perhaps curb protection), and parking is removed from Freeport south of the intersection. There are some safety benefits to these changes, but nowhere near as much as a roundabout or protected intersection would offer. Is there space for a roundabout here? Possibly. It would require using some of what is private land on the southwest corner and the east side, but there are no buildings, only parking lots, in the area needed.

Freeport - Sutterville Rd W intersection proposed
Freeport – Sutterville W intersection, north is to the right

And now, the Freeport – Fruitridge intersection. I’ve already made comments on this in the photo essay, but to repeat and look more closely… This is what it looks like today. There are intersections like this along every arterial in the south Sacramento, both city and county. A vast area of pavement, flared out at the intersection in favor of right and left turn lanes, designed to promote the flow of motor vehicle traffic, and designed with little thought to walkers and bicyclists. Of course volumes of bicyclists are new since these were built, but volumes of walkers are not new, they have always been here but were intentionally ignored by the planners and engineers.

Freeport - Fruitridge intersection existing
Freeport – Fruitridge intersection existing

And the intersection proposed by the plan. Other than being rotated 90 degrees, there is no significant difference. Green bicycle markings through the intersection? For what purpose? The purpose of green paint is to signify conflict zones, but the green in the intersection is not a conflict zone. Courageous bicyclists are not going to be encouraged nor protected by this green paint, and other bicyclists are just going to pray.

Every dedicated right turn lane is still there. Every dedicated left turn lane is still there, including the hazardous and unnecessary double left from Freeport southbound to Fruitridge eastbound.

Have median islands wide enough to be, and designed to be, pedestrian refuge islands on these long crossings, been added? No.

Freeport - Fruitridge intersection proposed
Freeport – Fruitridge intersection proposed, north to the right

There is enough space here for a roundabout. Or maybe a protected intersection would be better. I’m not sure, but what I do know is that the intersection design proposed by the city is just plain unacceptable. The community asked for safety, walkability, and economic vitality. This intersection design offers none of those things.

Roundabouts and traffic circles

It is common for people to use the terms roundabout and traffic circle interchangeably, as though there is no difference between the two. Sadly, Streetsblog San Francisco, whose mission is to educate the public, claims that there is no significant difference and that it is OK to use the terms interchangeably (SFMTA Launches “Muni Backwards” Program). That is not true.

A roundabout has two very significant features:

  1. significant horizontal deflection which slows traffic
  2. yield signs at all approaches

Traffic circles do not usually have these features.

Sac_7th-St_roundabout
roundabout, Sacramento

The photo at right shows a roundabout in the River District/Township 9 in Sacramento. It is quite a bit bigger than a roundabout needs to be, and was installed in a new development, not at an existing intersection, but you can see the deflection and yield signs.

Significant horizontal deflection means that vehicles must change significantly from a straight line of travel, which requires that they slow significantly. This slowing reduces the number of crashes somewhat, and almost eliminates the number of severe crashes and fatalities (about 80% reduction). They are safer because they greatly reduce the number of conflict points in an intersection.

R6-5_288Yield signs on all approaches means that vehicles only have to stop for other vehicles already in the roundabout. Otherwise, they proceed at their reduced speed and never have to stop. This yield approach benefits motor vehicles and bicyclists who ride in the travel lane. It does not, and is not really intended to, benefit bicyclists in bike lanes or pedestrians, but at the same time, if does not hurt them. There is one standard MUTCD sign used at roundabouts, shown at right, but you will also see many other signs at both roundabouts and traffic circles.

traffic circle, Sacramento

Traffic circles vary widely in size, and therefore the amount of deflection. At least in California, they almost always have stop signs on two of the approaches, so that one street does not stop and the other does. The photo at right shows a traffic circle in downtown Sacramento. It has some deflection, but not enough to really slow traffic, and with the stop sign, does not ease the flow of traffic. These traffic circles also squeeze bicyclists who do not know they need to take the lane to safety navigate the intersection. The traffic circle sign is not a federal or state standard sign, but does communicate.

There are a a number of traffic circles in Sacramento central city, most of which were put in years ago, but a few newer ones also exist. Depending on the size of the circle, they have varying traffic calming benefits. The reason traffic circles are used instead of roundabouts is that you can’t just plop a roundabout into the footprint of an existing urban intersection. They require more space.

There are a lot more features of roundabouts than just the two that I mentioned. If you want to become a traffic nerd on roundabouts, I recommend the FHWA roundabout page, particularly the publication Roundabouts: An Informational Guide, Second Edition. For an international best practices perspective that focuses on bicyclist benefits, check Explaining the Dutch roundabout abroad.

Multi-lane roundabouts probably do not have significant safety outcomes over regular intersections. Many Sacramento people have experienced multi-lane roundabouts in Roseville and in Truckee at the Interstate 80 – Hwy 89 interchange. It makes me nervous to even watch these, and I always label these as multi-lane roundabouts to distinguish them from single-lane roundabouts or just roundabouts, which do have very significant safety outcomes.

SF_new-traffic-circle-McAllister-LyonLastly, the type of traffic circle that engendered the discussion in San Francisco is at right. It has several non-standard features, even given the variability of traffic circles.

What are stop signs for? Part 2

Continued from Part 1

Streets should be designed to induce traffic speeds that are appropriate to that street, consistent with surrounding uses. In my mind, that means 20 mph in residential areas and up to 30 mph in commercial areas. What about all those other roadways? They are mis-designed stroads. Properly designed streets:

  1. have a grid pattern so that use is spread out rather than concentrated on a few streets, so that intersections may functions without stop sign or signal control
  2. have good visibility at intersections
  3. have both physical constraints and visual clues to ensure that they are used at the intended speed
  4. have a minimum of signs

Of course that is largely not what we have now. What to do?

r1-2The solutions to an excess of stop signs are:

  1. Roundabouts, covered in my previous post What is a roundabout?
  2. Spread out traffic by installing traffic calming equally on parallel streets, rather than focusing traffic on select streets by installing traffic calming on other streets.
  3. Change intersections to increase visibility, by modification or removal or vegetation, fences, and parking.
  4. Replace four-way stops with two-way stops where there are sufficient gaps in traffic on the busier street.
  5. Replace both four-way and two-way stops with two-way yields, with the yield signs being on the lower traffic street.
  6. Remove all signs from low traffic streets, and allow vehicles normal yielding behavior at the intersection.
  7. Analyze all intersections over time to assess whether signing is really necessary, with the default assumption being that it is not.

I suspect that after analyzing intersections for the purpose of the stop sign, and alternate solutions, the number of stop signs would be reduced by at least 60%. Safety would not be reduced. Speeds would not increase. Both motor vehicle drivers and bicycle drivers would be happier.

What is a roundabout?

I have noticed a lot of confusion in Sacramento amongst both transportation professionals and citizens interested in traffic calming about roundabouts. If you live, work or play in downtown and midtown Sacramento, you’ve seen a lot of structures in the intersections which people call roundabouts, but which are not, they are traffic circles. So what is a roundabout?

intersection conflict points
intersection conflict points

A modern roundabout is a structure that allows a free flow of traffic without stop signs. Instead, they use yield signs and markings. They are most appropriately used at street intersections where both streets are fairly busy. The biggest advantage of a roundabout, for all users, is the reduction of conflict points in the intersection from thirty-two to four, as illustrated in the diagram at right!

Continue reading “What is a roundabout?”