Ramps in Car Parks
frequent topic on my ‘Ask the Expert’ web pages is the gradient of vehicle
ramps in car parks!
and architects are trying to maximise the parking capacity of a ‘cube’ they
inevitably explore the scope for short ramps and low floor to ceiling
clearances. This leads to:
The question: What is the maximum gradient for a car park ramp?
And the response: It
the complexity of ramps in car parks one has to recognise that there are many
types of ramps used in many different situations.
Connecting ramps ramps
linking vertically separated parking decks as commonly found in multi-storey
Parking ramps ramps
combining the functions of circulation and storage as occur in spiral or
helical car parks
Whether a ramp
is curved or straight has an important bearing on the issue of gradient. Spiral
ramps used to connect different levels within a car park are curved and longer
than straight ramps serving the same purpose.
The following questions need to be answered before
considering ramp designs queries:
Is the car
park open to the public or used by only one group, e.g. staff?
ramp be used both by pedestrians and vehicles?
shopping trolleys, buggies, bicycles, scooters, motorbikes use the ramp?
car park have to cater for a broad spectrum of vehicle types or just a narrow
The ramp design limitations for a general purpose
public car park at a shopping centre, for example, are very different to those
for a car park built only to accommodate one type of vehicle, e.g. as might
happen at a car manufacturing location.
slope for straight ramps in situations such as:
car parks where the vertical separation between decks is less than 1.5m, is 1:6. This relatively steep slope is only possible
when using transition gradients top and bottom.
vertical differences are greater than 1.5m, is not less than 1:10.
ramps are curved, 1:10 or 1:12 depending on the separation.
Many modern cars have wheel bases that are ….. long and under-body clearances of less than…
The effect of these specifications is that in any situation where a ramp of
gradient steeper than 1:10 intersects with a flat slab that cars will bottom
out on the transition line at the top of the ramp. Figure 1.
The other side
of this phenomenon occurs at the bottom of ramps. Long tall vehicles moving off
a ramp onto a flat deck effectively rise up within the car park structure and
run the risk of striking the soffit or structural beams at the bottom of the
ramp. Figure 2.
In a car park
where members of the public are likely to walk on ramps, then any gradient
steeper than 1:10 is likely to be problematic.
wearing shoes with elevated heels finds steep slopes very uncomfortable and
pushing shopping trolleys, buggies or even bicycles find steep ramps very
uncomfortable and in many cases dangerous.
with mobility challenges requiring aids such as walking sticks, crutches or
wheelchairs experience severe difficulties on ramps steeper than 1:12.
To address some
of these issues, engineers have developed three stage ramp structures:
and the bottom of the ramp are constructed to a gentle gradient say 1:16 or
central section of the ramp is built to a steeper slope – 1:8 or 1:10.
additional issues with car park ramps include the:
to edge width
turning circle on approach routes to the bottom or from the top of ramps.
location of ticket machines on ramps
find ramps too narrow and scrape their bumpers along walls at the top or bottom
of ramps. The recommended minimum width for a one-way ramp is 3.0m with an
additional 0.3m for side clearance to the structure. The recommended width of
the entry section for a turning approach to a ramp is 3.5m. Bearing in mind
that very few cars are more than 1.8m wide these recommendations allow for a
broad range of driver behaviour and skills.
turning circles in car parks depend on the types of vehicles using them. Some
modern cars have turning circles of radius 6.0m to 7.5m. If these have to be
accommodated in a car park then it is prudent to design turning lanes on the
basis of an outside kerb radius of 9.0m. It is highly desirable that there are
no structural columns located at the turning pints onto or from ramps. They
intimidate drivers and lead to damage to walls and vehicles.
It is undesirable to have ticket machines located
on ramps, as drivers and vehicles experience difficulties. Practical experience
suggests that ticket machines on down ramps can work well while those on
up-ramps are generally unfriendly. On the down ramp the driver can see the
barrier in front and can respond to any slippage. There is little risk of
collision with another vehicle. On an up ramp the driver has very poor views of
cars behind and will be nervous in case his car drifts back or the car behind
gets too close. Handbrake starts on up ramps make many drivers nervous
designing ramps in car parks, it is vital that clear sight lines are maintained
at the top and bottom of the ramps. These are essential to the safety of
pedestrians and vehicles alike. The driver of a car on a ramp cannot readily
see directly in front because the bonnet of the car intrudes, and as a
consequence must depend on being able to see to the side to ensure he/she can
proceed safely. Curtain walls on ramp sides have been built with large holes to
provide very good sight lines.
of Structural Engineers excellent publication “Design Recommendations for
Multi-storey and Underground Car Parks” provides detailed information on many
aspects of car park ramp gradients. I have used their recommendations
throughout this paper. www.istructe.org.uk
Liam Keilthy is MD of Parking Consultants
Ltd., a specialist car park consultancy practice based in Dublin. He provides
‘Ask the Expert’ assistance on his web site at www.parkingconsultantsltd.com
Examples: A gradient of 1:10 represents
a steeper gradient than 1:12: