AARoads Forum

You're allowed to vote twice. I choose 60 and 70. 82 and 96 are nice, but the median doesn't necessarily have to be that wide.

Me and sprjus4 discussed about median sizes a few months ago, so let's talk about median sizes, shall we?

46 is good for an expressway, but in my opinion it's a little too small for a freeway.

60-70 is perfect IMO.

Quote from: tolbs17 on November 30, 2019, 06:16:42 PM
You're allowed to vote twice. I choose 60 and 70. 82 and 96 are nice, but the median doesn't necessarily have to be that wide.

In rural areas at least 60 feet. 

Fortyish and less, the slopes needed to establish proper drainage are too steep to be safely traversed by an errant vehicle.

With a 34-foot median like here, a guardrail median barrier was needed to keep vehicles from crossing the median, but that just creates a fixed object that vehicles can strike.
https://www.google.com/maps/@38.9279849,-76.0003737,88m/data=!3m1!1e3

For rural areas, 42-46 feet at minimum, preferably 60-70 feet or wider.

Anything ~50 feet or smaller should utilize at least a cable guardrail in the median to prevent median crossovers.

Here's an example (https://www.google.com/maps/@35.0676816,-78.1652954,3a,59.3y,156.32h,84.15t/data=!3m6!1e1!3m4!1s9CI4bftIazoh9d2DUKqLiQ!2e0!7i13312!8i6656) of a properly done 46 feet median on I-40 between Raleigh and Wilmington built throughout the 1980s and early 1990s with a continuous cable guardrail in the median. The posted speed limit is 70 mph. This is the standard design for rural freeway construction in North Carolina, though occasionally, such as on the under construction NC-540 project and the upcoming I-73 Rockingham Bypass, a wider 70 feet median is utilized. Even with a wider median of 70 feet, North Carolina will still utilize cable guardrail in the median (https://www.google.com/maps/@35.1357554,-79.7140915,3a,50.1y,12.22h,80.78t/data=!3m6!1e1!3m4!1s71oyOUOpgdJI5Nu5nA654Q!2e0!7i13312!8i6656) as an added precaution.

Texas has been taking a different approach to medians on new construction largely and instead utilizing 10 foot left paved shoulders and a jersey barrier dividing the lanes of traffic. Newer interstate highways such as I-69 within the state are being constructed like this, and future upgrade projects calls for maintaining this typical section for at least 40+ miles in areas. Here's an example (https://www.google.com/maps/@27.5718303,-97.7903482,3a,49.8y,21.2h,82.37t/data=!3m6!1e1!3m4!1sAoYQW40ni26uDlXA2NPAnQ!2e0!7i13312!8i6656) on a recently completed segment of I-69 outside Bishop (will not be signed until the Driscoll bypass is completed in 2022 linking to I-37). Not my ideal preference, but I feel like as long as a full left shoulder is provided to add "breathing" room, it doesn't pose any issues. I had more issues with the design until I actually drove on it, and it's actually not that bad aesthetics and design wise. In most cases, there are, but in some interchange projects (converting a single intersection into a grade-separated interchange), they've only provided a 4 foot left shoulder.

The one that prevents the most head-on accidents for that stretch of highway.

Quote from: Beltway on November 30, 2019, 11:51:21 PM
With a 34-foot median like here, a guardrail median barrier was needed to keep vehicles from crossing the median, but that just creates a fixed object that vehicles can strike.
https://www.google.com/maps/@38.9279849,-76.0003737,88m/data=!3m1!1e3

Always made me wonder - why did they use such a narrow median on that particular widening project? Where there associated right of way issues that prevented something such as 42 - 46 feet?

Quote from: sprjus4 on December 01, 2019, 12:16:31 AMTexas has been taking a different approach to medians on new construction largely and instead utilizing 10 foot left paved shoulders and a jersey barrier dividing the lanes of traffic. Newer interstate highways such as I-69 within the state are being constructed like this, and future upgrade projects calls for maintaining this typical section for at least 40+ miles in areas. Here's an example (https://www.google.com/maps/@27.5718303,-97.7903482,3a,49.8y,21.2h,82.37t/data=!3m6!1e1!3m4!1sAoYQW40ni26uDlXA2NPAnQ!2e0!7i13312!8i6656) on a recently completed segment of I-69 outside Bishop (will not be signed until the Driscoll bypass is completed in 2022 linking to I-37). Not my ideal preference, but I feel like as long as a full left shoulder is provided to add "breathing" room, it doesn't pose any issues. I had more issues with the design until I actually drove on it, and it's actually not that bad aesthetics and design-wise.

That looks like something they'd do where and only where the footprint is hemmed in by existing frontage roads, with any extra median width coming at the expense of the outer separation.

A lot of narrower medians in the U.S. (especially on Interstates) are equipped at minimum with what Gene Van termed "wait-a-minute cables" and at the highest a barrier that is often tall enough to block out oncoming headlights.

Quote from: sprjus4 on December 01, 2019, 12:30:52 AM

Quote from: Beltway on November 30, 2019, 11:51:21 PM
With a 34-foot median like here, a guardrail median barrier was needed to keep vehicles from crossing the median, but that just creates a fixed object that vehicles can strike.
https://www.google.com/maps/@38.9279849,-76.0003737,88m/data=!3m1!1e3

Always made me wonder - why did they use such a narrow median on that particular widening project? Where there associated right of way issues that prevented something such as 42 - 46 feet?

Most of the length they had a wide 4-lane right-of-way that was acquired when the MD-404 two-lane highway was built in the 1960s.

In these projects they built very wide storm water management channels on the outside of the 4-lane highway.  Visible on the Google Maps aerial view.

42 - 46 feet is still not a wide enough median to obviate need for a median barrier.

I enjoy larger medians.


Then again, I dream of someone building a freeway around a city, by running one direction on one side of town, and the other direction on the other side of town.

Quote from: Tom958 on December 01, 2019, 07:35:48 AM
That looks like something they'd do where and only where the footprint is hemmed in by existing frontage roads, with any extra median width coming at the expense of the outer separation.

Texas' approach is to reserve the outer space as future 6-lane widening. Often with these newer freeways, you'll have at least 40 feet or more between the edge of the mainline and the edge of the frontage road.

I-35 and I-10 had sections that were originally 4-lanes with a grassy median, and they reconstructed the freeway to still have only 4-lanes but with a median barrier and a large separation between the frontage road and the mainline. Then a few years later, they'd come back and reconstruct the torn up outside and voila - 6-lane freeway with median barrier. I-35 is like this the majority of the distance between Dallas and Austin as it's now a fully complete 6-lane interstate highway.

30 m (~100') at minimum.

What cracks me up is I-295 in Fayetteville from Cliffdale Rd to US-401 uses a 70 foot median compared to the rest of the highway which is 46 feet. I wonder why they did that...

And if you take a look at I-95 (especially the Fayetteville bypass and north of Kenly to the Virginia state line), there's a series of wide sections like here (https://www.google.com/maps/@35.8901809,-77.9370435,3a,69.6y,30.5h,87.7t/data=!3m6!1e1!3m4!1sM-iaLbCqTAFAH_4v9-rICw!2e0!7i16384!8i8192). I guess they do that on-purpose for safety reasons and to obstruct view from the other side I guess... Seems like in the 70s and 80s they loved building highways that way...

I-95 in Maryland (in the North East) area is 98 feet and is six lanes. I have to say, that's also a ultrawide median but going past the MD 272 interchange, it narrows to 52 feet. And when going into Delaware (Delaware Turnpike) it's 76 feet wide and eight lanes. If you compare this to recently completed I-85 in Concord, it's just a concrete barrier. I find this to be VERY interesting. And I know comparing this to the Delaware Turnpike, it's much more rural there (Well, maybe not in the Christiana area, cause that's slightly more urban, but kind of the same, really).

I'll put these medians from narrowest to widest.

22 feet - https://www.google.com/maps/@35.5350215,-78.2569675,3a,75y,67.09h,88.22t/data=!3m6!1e1!3m4!1sxHY4WjYmtAEFTbITY6_WhQ!2e0!7i16384!8i8192

36 feet - https://www.google.com/maps/@35.9755324,-77.9494406,3a,75y,290.48h,90t/data=!3m7!1e1!3m5!1sbYGZL5X7lFdizq_iwFvnxg!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DbYGZL5X7lFdizq_iwFvnxg%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D294.7779%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

46 feet - https://www.google.com/maps/@35.6088531,-77.4555017,3a,75y,270.35h,88.39t/data=!3m6!1e1!3m4!1s2zSOrSEAXj_5WVnqm4H93Q!2e0!7i16384!8i8192

60 feet - https://www.google.com/maps/@35.8177401,-77.0878092,3a,75y,253.02h,85.68t/data=!3m7!1e1!3m5!1sqmJg6EMAgTQLIgfPT9h7oQ!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DqmJg6EMAgTQLIgfPT9h7oQ%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D1.0153999%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

70 feet - https://www.google.com/maps/@35.7996732,-79.8403971,3a,75y,321.95h,83.66t/data=!3m7!1e1!3m5!1s27jCXtwMYy-eb3LqYyf7IA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3D27jCXtwMYy-eb3LqYyf7IA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D14.82189%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

84 feet - https://www.google.com/maps/@35.4009295,-79.768201,3a,75y,352.54h,85.87t/data=!3m7!1e1!3m5!1sz3iCJe9D7npPnI15ZIiDvw!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3Dz3iCJe9D7npPnI15ZIiDvw%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D294.85083%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

92 feet - https://www.google.com/maps/@34.9516696,-78.9010856,3a,75y,50.81h,92.77t/data=!3m7!1e1!3m5!1s0fTyhF0l-tL751aYqkCh6Q!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3D0fTyhF0l-tL751aYqkCh6Q%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D187.29237%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

96 feet - https://www.google.com/maps/@35.1575577,-77.2796602,3a,75y,84.48h,92.68t/data=!3m7!1e1!3m5!1sMkm2HO7EXy-6tMZwavcYwA!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DMkm2HO7EXy-6tMZwavcYwA%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D278.89624%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656

99-100 feet? - https://www.google.com/maps/@35.8926783,-79.6527784,3a,75y,334.6h,85.98t/data=!3m7!1e1!3m5!1shcT_z68umwkjfxHwsa56rQ!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DhcT_z68umwkjfxHwsa56rQ%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D222.55556%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192

I know these days they don't build new highways any wider than 70 feet at most.

In urban areas, smaller is better, with a concrete barrier separating the carriageways in the median.

As for rural settings, I'd prefer something at a minimum of 50 feet, with trees and/or hills in the median where possible. This way, there'd be a lower chance of head-on collisions.

Quote from: TEG24601 on December 01, 2019, 12:45:33 PM
I enjoy larger medians.


Then again, I dream of someone building a freeway around a city, by running one direction on one side of town, and the other direction on the other side of town.

Even though this does not qualify as a city per se, I-75's split around Arlington Heights, a northern Cincinnati suburb (https://www.google.com/maps/@39.2193971,-84.4413907,14.75z), might be what you're going for.

At least 90 feet, preferably more. Enough to grow trees in the middle to block oncoming headlights. Or put a river in the middle Montana does that in at least 2 places, and has a residence in the median of another.

Wide enough to have trees that block opposing headlights

Quote from: Henry on October 07, 2021, 10:51:40 AM
In urban areas, smaller is better, with a concrete barrier separating the carriageways in the median.

As for rural settings, I'd prefer something at a minimum of 50 feet, with trees and/or hills in the median where possible. This way, there'd be a lower chance of head-on collisions.

Quote from: TEG24601 on December 01, 2019, 12:45:33 PM
I enjoy larger medians.


Then again, I dream of someone building a freeway around a city, by running one direction on one side of town, and the other direction on the other side of town.

Even though this does not qualify as a city per se, I-75's split around Arlington Heights, a northern Cincinnati suburb (https://www.google.com/maps/@39.2193971,-84.4413907,14.75z), might be what you're going for.

See I-40 south of Raleigh and going down to Wilmington. It's all rural and yet it's ALL 46 feet. Does anyone think that's too narrow? In my opinion, it could have been 60 feet but it's fine I guess.

Quote from: HighwayStar on October 07, 2021, 03:02:27 PM
At least 90 feet, preferably more. Enough to grow trees in the middle to block oncoming headlights. Or put a river in the middle Montana does that in at least 2 places, and has a residence in the median of another.

In that case, I'm sure you're a huge fan of these (https://www.google.com/maps/@35.7972772,-78.1697665,3a,74.9y,287.62h,74.3t/data=!3m7!1e1!3m5!1sN_TkDO99jRxJT6OZO95rNg!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DN_TkDO99jRxJT6OZO95rNg%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D12.2802925%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192)!

As well as this (https://www.google.com/maps/@35.6301635,-78.1105715,3a,75y,35.92h,88.45t/data=!3m7!1e1!3m5!1sJeEwsYqZInnhPITe6S909Q!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DJeEwsYqZInnhPITe6S909Q%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D118.24929%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192).

And this (https://www.google.com/maps/@34.9669304,-78.8818183,3a,82.7y,53.08h,74.97t/data=!3m7!1e1!3m5!1sdW8At3a9WH9KGjeJtzO_6g!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DdW8At3a9WH9KGjeJtzO_6g%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D136.74036%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192).

And the most recent one done, this (https://www.google.com/maps/@35.6068302,-78.4510561,3a,75y,92.59h,86.41t/data=!3m6!1e1!3m4!1sHSPhQVZP42fiUIN5QzAs5Q!2e0!7i16384!8i8192).

When can we see more forested medians done?  :D

I am not a fan of the densely forested medians common on interstates in the Southeast. I find it quite tiring, even more so than traditional "boring" freeways such as I-80 or I-90 across the Plains. I think being able to see traffic heading the other direction really does help one keep awake.

I will say that the problem with building larger medians these days is that it requires more ROW, which is getting hard to acquire, especially when compared with when the interstate system was first built. I personally don't have much of an opinion on the subject.

I-55 in central IL was built with an 88-foot median in most places for the sections built in the mid-70's. By the time I-39 was built, prime farmland preservation was a thing, and after much negotiation, the corridor south of I-80 was built with a 54-foot median, but with specially designed bridges with no center pier. The first interstate in my area (I-80) was built on the cheap with a 40 foot median and has steep inner ditch slopes, and most of the corridor has been retrofitted with cable road guard to help prevent crossover head-on collisions as well as keeping at least one direction of traffic from crashing into the median ditch.

Quote from: Rick Powell on October 08, 2021, 12:26:51 AM
I-55 in central IL was built with an 88-foot median in most places for the sections built in the mid-70's. By the time I-39 was built, prime farmland preservation was a thing, and after much negotiation, the corridor south of I-80 was built with a 54-foot median, but with specially designed bridges with no center pier. The first interstate in my area (I-80) was built on the cheap with a 40 foot median and has steep inner ditch slopes, and most of the corridor has been retrofitted with cable road guard to help prevent crossover head-on collisions as well as keeping at least one direction of traffic from crashing into the median ditch.

With medians narrower than 60 feet, I say a cable barrier is definitely needed.

urban bypasses should be as narrow as safely possible, but out in the open area wider is much better. it's partially why I am loathe to take any of the current (and formerly signed) kentucky parkways.  the medians are narrow without any kind of barrier between them last time I checked and they look kind of steeply sloped as well. if kydot is so hellbent on making all the parkways 2di and 3di, in my opinion they need to work on the medians as well as correcting deficient and obsolete toll exit interchanges.

No true opinion on a "best" width, since there's probably a lot of factors in play when that's decided on a project.  Like, is the width selected at the time just for a wider median, or also possibly future ROW for widenings utilizing that median space.

I kinda like the Jersey median barriers, as long as there's a full left shoulder. Less right of way needed while maintaining room for emergencies on both sides.

I-64 just west of Richmond between Exits 181 and 183 is like this (actually there's room for another lane and at least a 4 foot shoulder)

I-84 between the CT border and MA 131 is perfect. :bigass:

Quote from: jp the roadgeek on October 08, 2021, 07:49:12 PM
I-84 between the CT border and MA 131 is perfect. :bigass:

How about I-85 that crosses over Hamby Creek in North Carolina?

As a driver, I don't really feel it is possible to have a median that is too wide in rural areas.  As median width increases, the amount of glare screening and roadside safety hardware that has to be provided goes down, while the options for securing satisfactory drainage (and resiliency during high-intensity rainfall) broaden.  But there are definitely tradeoffs in terms of ROW acquisition cost, taking land out of productive use, and span lengths for overbridges and other crossing structures.

Some states, such as Oklahoma, already provide cable barrier for medians as wide as 80 ft.  I expect this practice to become more common and, for this reason, I don't think a policy of providing wide medians expressly to eliminate the need for cable barrier will survive the test of time.

I-490 west of Rochester is an example of a roadway that was intentionally built with a very wide median to allow for future widening that was never needed (and likely never will be, especially west of Exit 4).

It's a great road on the whole, but as I've mentioned previously, I don't like long stretches where you can't see traffic going the other direction, and it does have a few of those.

My obvious preference would be for whatever is best engineeringwise for the location in question, but that's not really a fun answer. So, what I did is I went ahead and drew an Interstate highway, to scale, in Microsoft Paint, and moved the carriageways around until I found the median that looks best aesthetically, which turns out to be 40 feet, or 48 feet if you include the left shoulders, which median widths always do for some reason.

(https://i.imgur.com/0tz2QYq.png)

Quote from: CtrlAltDel on October 10, 2021, 11:39:21 AM
My obvious preference would be for whatever is best engineeringwise for the location in question, but that's not really a fun answer. So, what I did is I went ahead and drew an Interstate highway, to scale, in Microsoft Paint, and moved the carriageways around until I found the median that looks best aesthetically, which turns out to be 40 feet, or 48 feet if you include the left shoulders, which median widths always do for some reason.

(https://i.imgur.com/0tz2QYq.png)

Ikr, they couldn't just do the grass...

How about the one-and-a-half mile median along I-8 in Ocotillo?

As narrow as the standards permit, so standard width of the left shoulders + the width of the concrete barrier

Quote from: jamess on October 07, 2021, 04:02:11 PM
Wide enough to have trees that block opposing headlights

Barriers that are built high enough are also effective at blocking headlights. So about 25 feet (10 foot left shoulder on each side, leaving 5 feet for the barrier itself)

The UK pretty much always uses barriers and always has done, I think. In fact, that seems to be the done thing in most places outside North America. England current uses concrete "Jersey" barriers on medians. Until a decade or so back, metal barriers were used.

I'm OK with a Jersey barrier anywhere if it reduces ROW costs and expedites construction. Plus, it cuts down on smokey bears camping in the median....

Quote from: Mr Kite on October 21, 2021, 10:32:16 PM
The UK pretty much always uses barriers and always has done, I think. In fact, that seems to be the done thing in most places outside North America. England current uses concrete "Jersey" barriers on medians. Until a decade or so back, metal barriers were used.

Older parts of the German Autobahn used simple guard rails in the 1990s. I seem to remember more permanent barriers in urban areas.

Quote from: Road Hog on October 23, 2021, 02:14:00 AM
I'm OK with a Jersey barrier anywhere if it reduces ROW costs and expedites construction. Plus, it cuts down on smokey bears camping in the median....

But it's more expensive.

I forgot to mention that US-64 between Tarboro and Williamston has a series of transitioning between 46 feet and 60 feet. How cool is that?

Prior to the 1970s medians used to be very small like look at the Nashville, NC bypass (US-64)

Or I-95 between Kenly and Eastover.

Quote from: webny99 on October 07, 2021, 06:11:22 PM
I am not a fan of the densely forested medians common on interstates in the Southeast. I find it quite tiring, even more so than traditional "boring" freeways such as I-80 or I-90 across the Plains. I think being able to see traffic heading the other direction really does help one keep awake.

If you need oncoming traffic to keep you awake you are too damn tired to be driving and belong in a motel room.
What it does, which is a real benefit, is block oncoming headlights at night. And today with the stupid arms race of LED lights and no one having heard of a dimmer switch it is far more fatiguing to be blinded all the time than not see the oncoming traffic at all.

Wide medians are great for reserving future right of way, great if you need to add lanes or finally do the sensible thing and add service plazas to all interstates.
Also good for conversion into runways if needed.

Quote from: HighwayStar on January 25, 2022, 07:22:47 PM
Wide medians are great for reserving future right of way, great if you need to add lanes or finally do the sensible thing and add service plazas to all interstates.
Also good for conversion into runways if needed.

Yes, also not having to replace the bridges, like take a look at the Fayetteville bypass for instance or I-95 south of I-74.

Quote from: HighwayStar on January 25, 2022, 07:22:47 PM
Wide medians are great for reserving future right of way, great if you need to add lanes or finally do the sensible thing and add service plazas to all interstates.
Also good for conversion into runways if needed.

Service plazas should only be located in the median if under or over passes are provided so that traffic doesn't have to use left exits or entrances to access them.

Quote from: ran4sh on January 26, 2022, 05:56:46 PM

Quote from: HighwayStar on January 25, 2022, 07:22:47 PM
Wide medians are great for reserving future right of way, great if you need to add lanes or finally do the sensible thing and add service plazas to all interstates.
Also good for conversion into runways if needed.

Service plazas should only be located in the median if under or over passes are provided so that traffic doesn't have to use left exits or entrances to access them.

In a sufficiently low traffic area I don't see it as a problem. There are some in the northeast with the left ramp that should not have one, but in other areas it would be fine.

As seen in pages 22, 23, and 24 for North Carolina, 70 feet is usually preferred for new locations unless there's a protected area. 60 feet is for no future lanes required. Lastly 46 is for areas with protected areas such as wetlands, districts, etc.

Which is funny because I-40 was built with a 46 feet median between Clayton and Wilmington as well as between Hillsborough and Durham. Now it's overpopulated and needs many more lanes.

https://connect.ncdot.gov/projects/roadway/roadway%20design%20manual/01.%20general%20design.pdf