Parking lot design specifications 4

[maelstrom]

I have become enraged at the design of parking lots for nearby shopping centers/malls/etc. during the pre-Christmas shopping frenzy. After contemplating a while and consulting with a few other people, I have come to the conclusion that there is no such thing as a well-designed parking lot.

I know this can't possibly be true.

I set out to search the web. I found a few design mandates from the government in the form of the ADA Guidelines, a few specifications for asphalt bases and ground pre-conditioning, and that everything should have a 1/4 inch-per-foot grade for drainage. There was very little publicly-available information on this topic, only a few references to things such as Architectural Graphics Standards and asphalt manufacturers/associations. (the best thing I see:

http://www.apai.net,

Design Guide, Ch. 5)

Does such information exist at-large, or is it confined to trade publications/texts? If it does exist, pointers would be gladly accepted, i'll be putting up a reference page with everything I can find on parking lot design, traffic flow, etc.

Also, if anyone knows a "good" parking lot in the DC/MD/VA area, i'd love to hear about it.

 

[Ron]

Though it might not seem so, the design of a parking lot has a lot of variables to consider, many of which have nothing to do with the pavement.

Most traffic flow issues are related and controlled by area departments of transportation (particularly if the lot feeds a state road). The drainage may be impacted similarly. As for traffic flow within the lot, that depends typically on three groups...the owner (or owner's architect), the local land planning agency, and the civil engineer. The ADA plays into this, but is accommodated pretty easily under most reasonable flow scenarios.

The number of spaces is dictated by land planning codes/ordinances. The type of spaces, except accessible spaces, is also dictated. From there, the geometry of the lot is usually decided by the architect to complement the building. The civil engineer then takes the hand he's dealt and plays his game for space layout, islands, traffic markings, drainage, etc.

Long way to answer your bottom line question, huh? The bottom line is that parking lots have no universal design criteria and are often subject to local whimsey and the capability of the civil engineer.

 

[KThomson]

Hello!

Well - in New Jersey at least - usually each town has its own standards in the ordinance.

Parking spaces vary anywhere from 9'x18' to 10'x20'.

(There is also a practice that I think is being discouraged of having "compact spaces" like 8'x17' marked and designated for "compact" cars)

The typical standard around here for an aisle width for two way traffic, perpendicular spaces, is 24'.

I can't think of one publication that has everything you want - but here are some references

1- New Jersey Residential Site Improvement Standards (Free online - can't find it at the moment, I can email it to you if necessary)

2- Civil Engineering Reference Manual (CERM) by Lindeburg (not free)

My previous boss used to refer to cross slopes in parking lots greater than 5 or 6% as "door slamming" slopes - meaning your car door will slam shut when you get out.

Hope this helps a little!

Kate

 

[KRSServices]

You are right, there is no good design. Unfortunately, most municipalities specify an number of parking stalls in relation to a particular density or landuse of the site, ie: mall or restaurant. Since a developer usually intends to maximize the area for building space, parking lots tend to be very tight in terms of maneouverability. I have witnessed parking lot spacing premised entirely on smaller vehicles, and was accepted by the approving municipality. The bottom line is that the jurisdiction and control is really vested with the owner. In the case of a mall, if parking is too tight, then it is up to the owner to accomodate complaints or otherwise lose business. Drainage and sloping are generally pretty straight forward, but stall area and aisle width are always problems. KRS Services

http://www.krs-services.com

 

[Ron]

Kate...you gave a good example of an incompatibility between parking lot specifications and practicality. Many land planning ordinances, recommended practices, and engineering experiences tell the designer to get the water off quickly so set the slopes high. Many designers want 2-3% slopes to accomplish this. Some will allow the "door slamming slopes", though if they think about it their liability goes up when they do this (slip and fall, etc.).

The ADA sets the max at 2%. Where I live, slopes of 0.5% to 1% are common (Southeast US, coastal plains).

Stay with common sense and engineering judgment...they usually serve one pretty well.

 

[gibfrog]

There are many design guides for parking lots -

Two reference manuals from the National Parking Association are found here -

http://www.npapark.org/08_pubs_01.html

There are multiple sites in the "parking" section of

http://www.trafficlinq.com/

A brief intro to parking lots can be found here

http://www.webs1.uidaho.edu/niatt_labmanual/

The ITE (Institute of Transportation Engineers)has several books in their bookstore at

http://www.ite.org/bookstore/pubsalpha.pdf

Check out "parking under p" but there are 59 pages of books and stuff.

Everyone has given you good advice. There is the traffic flow aspect, the drainage aspect, the landscaping aspect, the ADA aspect and the user friendly aspect (a snow removal aspect up north). This is an evolving field and we now have higher expectations of parking lots. However, during the Christmas season, parking lots are at peak capacity, drivers are running red lights and behaving badly. Clifford H Laubstein
FL Certified PE #58662

 

[jheidt2543]

This is only a little off topic. In our area, they have passed a new zoning ordinance that, along with many other things, specifies the landscaping requirments in and around parking lots. They assign each type of tree, bush and flowering plant points and the developer/designer must have so many points of each type of plant in their landscaping plan. This ordinance has more than doubled the landscaping budgets for new developments in our city! Not to mention the amount of maintenence these require.

I like "trees and bushes and flowers and things" but, this is a monster. It must have been written by the landscape lobby! In all cases, it requires planting islands in the parking lot, no matter what size the lot is. In this part of the country, where we get snow in the winter, the islands are real plow breakers when trying to clear out the snow. Yes, trees are nice, but how about some practicality in these things too?

 

[maelstrom]

I didn't even know there was such a thing as the National Parking Association! That's exactly the kind of thing i've been looking for. Also, I guess I should be looking at Traffic Engineering, as that seems to be where more information on parking can be found.

Great sites, good references. I'll be posting some info to

http://www.dullsville.com/parking.php

sometime this week, with this info and others that I have found.

And, as Mr. Laubstein said, road rage (or mall rage?) peak season is now past, so it's not nearly as pressing. I'm off to the local library to see what they have from the ITE list.

 

[gibfrog]

A few final words -

Check out parking garage design for the concept of LEVEL OF SERVICE as it applies to parking garages, many items as applicable to parking lots. Size of spaces, drive isles, slopes, radii, etc.. (I learned about the 6% slope rule for older drivers and vehicle door control while studying garages, the 10% rule for pedestrian walkways, the 12% rule for fork lifts and the 16% rule for older drives on ramps. I live and design in Central Florida and slopes under 1%-2% are the norm)

Remember, that people must walk from the parking space to the building entrance and pedestrians must cross the driveways at the property line on the sidewalk in the public right-of way. Think pedestrian safety.

Think about visibility triangles at intersections, not the 15'x15' zoning crap, but your local DOT "Green Book" (Manual of uniform minimum standards for streets and highways) requirements.

Remember the "clear zone" concept from the "Green Book". Keep trees & signs a minimum of 2.5' off the edge of pavement for driveways. Also think about throat depths and deceleration lanes.

For trucks, think compound radii. Design for tired, lazy truckers or you will be replacing curbing, trees, signs, bushes, etc.

Follow the MUTCD for all traffic control. Use yellow lines to separate opposing traffic. Use standard signage.

Sure, any engineer can design a parking lot. Just follow your local zoning regulations and common sense. How many can design a good one? Clifford H Laubstein
FL Certified PE #58662

 

[trafficPro]

One of the most important aspects that should be understood in fending off complaints about parking supply, is that there is not, and should not be, an intention to fulfill every parking demand.
To do so would result in an excess of parking spaces during most of the year. It would also incur excess drainage problems, as well as being wasteful of the land area, (an asset).

The design lot capacity is intended to meet the 30th highest hour. So dont be surprised if Christmas shopping parking is a bear. The inability to find parking almost immediately results in either a tedious circling of the lot, or a move to another commercial facility.
An unsafe design, on the other hand can cause pedestrian accidents, and fender benders.
Also understand, if the lot you are in is crowded on Christmas, so is the lot you are thinking of switching to.
If possible, design the facility so trucks and cars dont mix much. Also, due to building rear setback requirements, many designs feature parking in the rear of the buildings. They count towards your ordinance requirement, but dont help the site at all. Unless owner operated, most large stores do not allow employees to use rear exits, as shoplifting concerns mount. Examine the large commercial centers in your area. Take a look at the parking spaces delineated in the rear of the building. Most are almost totally devoid of parkers.
I've been reviewing commercial developments for planning board for years, and the towns that take my advice dont permit the counting of rear parking spaces over 5% of the total required. Even that was a compromise.)5 would have been better. If special circumstances indicate that rear parking would be used due to open passages thru the buildings, then the board has the option to permit the counting of those spaces.
TrafficPro

 

[danny2000]

Iam looking for any info on the geometric design of parking lots and also urban land economic's for a college project
cheers
Dan..Ireland