Apache 2.4 has a module called mod_ratelimit. This module gives you the ability to limit the bandwidth of your requests posted to the web server. The usage is quite simple (read the docs):

First load the module (Apache 2.4 on FreeBSD). Uncomment following line in /usr/local/etc/apache24/httpd.conf

LoadModule ratelimit_module libexec/apache24/mod_ratelimit.so

This will load the module during next startup. Now how do i use it? Well, let's say you want the whole server to limit every request to 5MB/s, then use this:

<IfModule mod_ratelimit.c>
    SetOutputFilter RATE_LIMIT
    SetEnv rate-limit 5120
</IfModule>

The same can be applied to only specific directories if you need to:

<IfModule mod_ratelimit.c>
    <Location "/downloads">
        SetOutputFilter RATE_LIMIT
        SetEnv rate-limit 5120
    </Location>
</IfModule>

Last step, as apache needs to load a new module, restart your webserver, not reload:

# service apache24 restart